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Exhibit 12.1 Certification of the Chief Executive Officer I, Eric Meurice, certify that:  1.
    I have reviewed this annual report on Form 20-F of ASML Holding N.V.;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 statement 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 company as of, and for, the periods presented in this report;4.
    The company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 company 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 company, 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 company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; andc)
    Disclosed in this report any change in the companys internal control over financial
reporting that occurred during the period covered by the annual report that has materially
affected, or is reasonably likely to materially affect, the companys internal control over
financial reporting; and  5.
    The companys other certifying officer(s) and I have disclosed, based on our most recent
evaluation of internal control over financial reporting, to the companys auditors and the
audit committee of the company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 companys ability to record, process, summarize and report financial information; andb)
    Any fraud, whether or not material, that involves management or other employees who
have a significant role in the companys internal control over financial reporting. Date: January 28, 2005 /s/ Eric Meurice,
Chief Executive Officer




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Certification of the
Chief Financial Officer I, Peter T.F.M. Wennink, certify that:  1.
    I have reviewed this annual report on Form 20-F of ASML Holding N.V.;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 statement 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 company as of, and for, the periods presented in this report;4.
    The company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 company 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 company, 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 company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; andc)
    Disclosed in this report any change in the companys internal control over financial
reporting that occurred during the period covered by the annual report that has materially
affected, or is reasonably likely to materially affect, the companys internal control over
financial reporting; and  5.
    The companys other certifying officer(s) and I have disclosed, based on our most recent
evaluation of internal control over financial reporting, to the companys auditors and the
audit committee of the company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 companys ability to record, process, summarize and report financial information; andb)
    Any fraud, whether or not material, that involves management or other employees who
have a significant role in the companys internal control over financial reporting. Date: January 28, 2005 /s/ Peter T.F.M. Wennink
Chief Financial Officer