Exhibit31.1

CERTIFICATION PURSUANT TO SECTION 302 OF THESARBANES-OXLEY ACT OF 2002

I, William H. Joyce, certifythat:

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| 1.  | I have reviewed this annualreport on Form 10-K of Nalco HoldingCompany; |

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| 2.  | Based on my knowledge,this report does not contain any untrue statement of a material fact oromit to state a material fact necessary to make the statements made, inlight of the circumstance under which such statements were made, notmisleading with respect to the period covered by thisreport; |

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| 3.  | Based on my knowledge, thefinancial statements, and other financial information included in thisreport, fairly represent in all material respects the financialcondition, results of operations and cash flows of the registrant asof, and for, the periods presented in thisreport; |

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| 4.  | The registrant'sother certifying officer and I are responsible for establishing andmaintaining disclosure controls and procedures (as defined in ExchangeAct Rules 13a-15(e) and 15d-15(e)) for the registrant andhave: |

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| (a)  | Designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to bedesigned under our supervision, to ensure that material informationrelating to the registrant, including its consolidated subsidiaries, ismade known to us by others within those entities, particularly duringthe period in which this report is beingprepared; |

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| (b)  | Evaluated the effectiveness ofthe registrant's disclosure controls and procedures and presentedin this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period coveredby this report based on such evaluation;and |

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| (c)  | Disclosed in this report any change inthe registrant's internal control over financial reporting thatoccurred during the registrant's most recent fiscal quarter (theregistrant's fourth fiscal quarter in the case of an annualreport) that has materially affected, or is reasonably likely tomaterially affect, the registrant's internal control overfinancial reporting; and |

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| 5.  | Theregistrant's other certifying officer and I have disclosed, basedon our most recent evaluation of internal control over financialreporting, to the registrant's auditors and the audit committeeof the registrant's board of directors (or persons performing theequivalent functions): |

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| (a)  | All significantdeficiencies and material weaknesses in the design or operation ofinternal control over financial reporting which are reasonably likelyto adversely affect the registrant's ability to record, process,summarize and report financial information;and |

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| (b)  | Any fraud, whether or not material,that involves management or other employees who have a significant rolein the registrant's internal control over financialreporting. |

Date: March 24, 2005

/s/ William H. Joyce Name: William H.Joyce Title: Chairman and Chief ExecutiveOfficer

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