EXHIBIT 31 (a)

I, James Dimon, certify that:

| | 1. | I
have reviewed this quarterly report on Form 10-Q of Bank One 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(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:
| | -- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

| | (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(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.
| | --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------

November 6, 2003

| |  | /s/ James Dimon
James DimonPrincipal Executive Officer
| |  | --------------------------------------------------------------------

76

---