EXHIBIT 31.1

                                 CERTIFICATIONS

I, John R. Irwin, certify that:

1.          I have reviewed this annual report on Form 10-K of Atwood
            Oceanics, Inc.;

2.          Based on my knowledge, this 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 report;

3.          Based on my knowledge, the financial statements, and other
            financial information included in this 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 report;

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)) and internal control over financial
            reporting (as defined in Exchange Act Rules 13a-15(f) and
            15d-15(f)) for the registrant and have:

            (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;

            (b) Designed such internal control over financial reporting to
            be designed under our supervision, to provide reasonable
            assurance regarding the reliability of financial reporting and
            the preparation of financial statements for external purposes
            in accordance with generally accepted accounting principles;
            and

            (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

            (d) Disclosed in this report any change in the registrant's
            internal control over financial reporting that occurred during

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            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

5.          The registrant's other certifying officer(s) and I have
            disclosed, based on our most recent evaluation of internal
            control over financial reporting, to the registrant's auditors
            and the audit committee of the registrant's board of directors
            (or persons performing the equivalent functions):

            (a) All significant deficiencies and material weaknesses in
            the design or operation of internal control over financial
            reporting which are reasonably likely to adversely affect the
            registrant's ability to record, process, summarize and report
            financial information; and

            (b) Any fraud, whether or not material, that involves
            management or other employees who have a significant role in
            the registrant's internal control over financial reporting.

Date: December  14, 2005

                  /S/ JOHN R. IRWIN
                  John R. Irwin
                  Chief Executive Officer