EX-31.1: CERTIFICATION
Published on May 7, 2007
    Exhibit 31.1
    Certification
    I, E. Stanley ONeal, certify that:
    1. I have reviewed this quarterly report on
    Form 10-Q
    of Merrill Lynch & Co., 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 registrants 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, or caused 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;
    (c) Evaluated the effectiveness of the registrants
    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
    registrants internal control over financial reporting that
    occurred during the registrants most recent fiscal quarter
    (the registrants fourth fiscal quarter in the case of an
    annual report) that has materially affected, or is reasonably
    likely to materially affect, the registrants internal
    control over financial reporting; and
    5. The registrants other certifying officer(s) and I
    have disclosed, based on our most recent evaluation of internal
    control over financial reporting, to the registrants
    auditors and the audit committee of the registrants 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
    registrants 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
    registrants internal control over financial reporting.
/s/  E. Stanley
    ONeal
| E. Stanley ONeal | 
    Chairman of the Board and
    Chief Executive Officer
    Dated: May 7, 2007
    
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