Exhibit31.1

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

I, William H. Joyce,certify that:

|          |                                                                         |
|----------|-------------------------------------------------------------------------|
| 1.  | I have reviewedthis annual report on Form 10-K of Nalco HoldingCompany; |

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

|          |                                                                                                                                                                                                                                                                                      |
|----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 3.  | Based on my knowledge,the financial statements, and other financial information included inthis report, 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)) and internal control over financialreporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f))for the registrant andhave: |

|           |                                                                                                                                                                                                                                                                                                                                                                          |
|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (a)  | Designed such disclosurecontrols and procedures, or caused such disclosure controls andprocedures 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)  | Designed suchinternal control over financial reporting, or caused such internalcontrol over financial reporting to be designed under our supervision,to provide reasonable assurance regarding the reliability of financialreporting and the preparation of financial statements for externalpurposes in accordance with generally accepted accountingprinciples; |

|           |                                                                                                                                                                                                                                                                                      |
|-----------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (c)  | 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 |

|           |                                                                                                                                                                                                                                                                                                                                                                                                          |
|-----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (d)  | Disclosed in this reportany change in the registrant’s internal control over financialreporting that occurred during the registrant’s most recentfiscal quarter (the registrant’s fourth fiscal quarter in thecase 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’sother certifying 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 theequivalent functions): |

|           |                                                                                                                                                                                                                                                                            |
|-----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| (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, whether or notmaterial, that involves management or other employees who have asignificant role in the registrant’s internal control overfinancial reporting. |

Date: March 1, 2007

/S/ William H.Joyce                                                                Name:    William H. Joyce Title:        Chairman andChief Executive Officer

----