<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>2101100 - Disclosure - ORGANIZATION AND BASIS OF PRESENTATION:</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

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</LabelSeparator><Level>1</Level><ElementName>us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Organization, Consolidation and Presentation of Financial Statements [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_BusinessDescriptionAndBasisOfPresentationTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><PreferredLabelRole>terseLabel</PreferredLabelRole><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="D2013Q2YTD" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;div style="font-family:Times New Roman;font-size:10pt;"&gt;&lt;div style="line-height:120%;padding-top:12px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;font-weight:bold;"&gt;ORGANIZATION AND BASIS OF PRESENTATION:&lt;/font&gt;&lt;font style="font-family:inherit;font-size:8pt;"&gt;&amp;#160;&lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-top:12px;text-indent:32px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;SYNNEX Corporation (together with its subsidiaries, herein referred to as &amp;#8220;SYNNEX&amp;#8221; or the &amp;#8220;Company&amp;#8221;) is a business process services company offering a comprehensive range of services to resellers, retailers, and original equipment manufacturers (&amp;#8220;OEMs&amp;#8221;) worldwide. SYNNEX&amp;#8217;s business process services include wholesale distribution and business process outsourcing (&amp;#8220;BPO&amp;#8221;) services. SYNNEX is headquartered in Fremont, California and has operations in North America, Central America, Asia and Europe. &lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-bottom:6px;padding-top:6px;text-align:left;text-indent:30px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;The accompanying interim unaudited Consolidated Financial Statements as of &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:10pt;color:#000000;font-style:normal;font-weight:normal;text-decoration:none;"&gt;May&amp;#160;31, 2013&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt; and for the three and six month periods ended &lt;/font&gt;&lt;font style="font-family:Times New Roman;font-size:10pt;color:#000000;font-style:normal;font-weight:normal;text-decoration:none;"&gt;May&amp;#160;31, 2013&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt; and 2012 have been prepared by the Company in accordance with the rules and regulations of the Securities and Exchange Commission (&amp;#8220;SEC&amp;#8221;). The amounts as of &lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;"&gt;November&amp;#160;30, 2012&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt; have been derived from the Company&amp;#8217;s annual audited financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles (&amp;#8220;GAAP&amp;#8221;) in the United States have been condensed or omitted in accordance with such rules and regulations. In the opinion of management, the accompanying unaudited Consolidated Financial Statements reflect all adjustments, consisting only of normal recurring adjustments, necessary to state fairly the financial position of the Company and its results of operations and cash flows as of and for the periods presented. These financial statements should be read in conjunction with the annual audited financial statements and notes thereto as of and for the fiscal year ended &lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;"&gt;November&amp;#160;30, 2012&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;, included in the Company&amp;#8217;s Annual Report on Form 10-K for the fiscal year then ended. &lt;/font&gt;&lt;/div&gt;&lt;div style="line-height:120%;padding-top:12px;text-align:left;text-indent:30px;font-size:10pt;"&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt;The results of operations for the three and six months ended &lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;color:#000000;text-decoration:none;"&gt;May&amp;#160;31, 2013&lt;/font&gt;&lt;font style="font-family:inherit;font-size:10pt;"&gt; are not necessarily indicative of the results that may be expected for the fiscal year ending November&amp;#160;30, 2013, or any future period and the Company makes no representations related thereto.&lt;/font&gt;&lt;/div&gt;&lt;/div&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for the business description and basis of presentation concepts.  Business description describes the nature and type of organization including but not limited to organizational structure as may be applicable to holding companies, parent and subsidiary relationships, business divisions, business units, business segments, affiliates and information about significant ownership of the reporting entity.  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