US ONCOLOGY HOLDINGS, INC. AND US ONCOLOGY, INC.

EXHIBIT 31.2

CERTIFICATION

US Oncology Holdings, Inc. and

US Oncology,
Inc.

I, Richard P. McCook, certify that:



|(1) | I have reviewed this quarterly report on Form 10-Q of US Oncology Holdings, Inc. and US Oncology, Inc.;
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|(2) | Based on my knowledge, this quarterly report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the
statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this quarterly report;
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|(3) | Based on my knowledge, the financial statements, and other financial information included in this quarterly report, fairly present in all material respects the
financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this quarterly report;
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|(4) | The registrants other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant and have:
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| | (a) | designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material
information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;
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| | (b) | [intentionally omitted];
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| | (c) | evaluated the effectiveness of the registrants disclosure controls and procedures and presented in this report our conclusions about the effectiveness of
the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and
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| | (d) | disclosed in this report any change in the registrants internal control over financial reporting that occurred during the registrants most recent
fiscal quarter (the registrants fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrants internal control over financial reporting; and
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|(5) | The registrants other certifying officer and I have disclosed, based on our most recent evaluation, to the registrants auditors and the audit
committee of registrants board of directors (or persons performing the equivalent function):
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| | (a) | All significant deficiencies in the design or operation of internal controls which could adversely affect the registrants ability to record, process,
summarize and report financial data and have identified for the registrants auditors any material weaknesses in internal controls; and
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| | (b) | any fraud, whether or not material, that involves management or other employees who have a significant role in the registrants internal controls.
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|Date: August 10, 2006 |  | By: |  | /s/ RICHARD P. McCOOK                                                                                   
|                      |  |     |  | Richard P. McCook,                                                                                      
|                      |  |     |  | Executive Vice President and Chief
Financial Officer of US Oncology Holdings, Inc. and US Oncology, Inc.