##### 



Exhibit 31 Certifications I, Don J. McGrath certify that: 1. I have reviewed this report on Form 10-Q of BancWest Corporation; 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 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: 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) 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 c) 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 5. The registrants other certifying officer 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.

        . /s/ Don J. McGrath
Don J. McGrath
President and Chief Executive Officer Date: May 13, 2005




---



##### 



Exhibit 31 Certifications I, Douglas C. Grigsby, certify that: 1. I have reviewed this report on Form 10-Q of BancWest Corporation; 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 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: 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) 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 c) 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 5. The registrants other certifying officer 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. /s/ Douglas C. Grigsby
Douglas C. Grigsby
Executive Vice President, Chief Financial Officer and Treasurer Date: May 13, 2005