Exhibit31.1

CERTIFICATION PURSUANT TOSECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, WilliamH. Joyce, certify that:

|          |                                                                            |
|----------|----------------------------------------------------------------------------|
| 1.  | I havereviewed this quarterly report on Form 10-Q of Nalco HoldingCompany; |

|          |                                                                                                                                                                                                                                                                                                    |
|----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 2.  | Based on my knowledge,this report does not contain any untrue statement of 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; |

|          |                                                                                                                                                                                                                                                                                       |
|----------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 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; |

|          |                                                                                                                                                                                                                         |
|----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 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: |

|  |           |                                                                                                                                                                                                                                                                                                                                                                          |
|--|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|  | (a)  | Designed suchdisclosure controls and procedures, or caused such disclosure controlsand procedures to be designed under our supervision, to ensure thatmaterial information relating to the registrant, including itsconsolidated subsidiaries, is made known to us by others within thoseentities, particularly during the period in which this report is beingprepared; |

|  |           |                                                                                                                                                                                                                                                                                |
|--|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|  | (b)  | Evaluated theeffectiveness of the registrant's disclosure controls andprocedures and presented in this report our conclusions about theeffectiveness of the disclosure controls and procedures, as of the endof the period covered by this report based on such evaluation;and |

|  |           |                                                                                                                                                                                                                                                                                                                                                                                  |
|--|-----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|  | (c)  | Disclosed in thisreport any change in the registrant's internal control overfinancial reporting that occurred during the registrant's mostrecent fiscal quarter (the registrant's fourth fiscal quarter inthe case of an annual report) that has materially affected, or isreasonably likely to materially affect, the registrant's internalcontrol over financial reporting;and |

|          |                                                                                                                                                                                                                                                                                           |
|----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 5.  | The registrant's othercertifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to theregistrant's auditors and the audit committee of theregistrant's board of directors (or persons performing theequivalentfunctions): |

|  |           |                                                                                                                                                                                                                                                                      |
|--|-----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|  | (a)  | Allsignificant deficiencies and material weaknesses in the design oroperation of internal control over financial reporting which arereasonably likely to adversely affect the registrant's ability torecord, process, summarize and report financial information;and |

|  |           |                                                                                                                                                                         |
|--|-----------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|  | (b)  | Any fraud, whetheror not material, that involves management or other employees who have asignificant role in the registrant's internal control overfinancial reporting. |

Date: November 10, 2005

/s/ WILLIAM H.JOYCE                                        Name:  William H. Joyce Title:    Chairman andChief Executive Officer

----