EXHIBIT31(i).1

CERTIFICATION OF PERIODIC REPORT UNDERSECTION 302 OFTHE SARBANES-OXLEY ACT OF 2002

I, A. E. Festa, certify that:

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| 1.  | Ihave reviewed this annual report on Form 10-K of W. R. Grace &Co.; |

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| 2.  | Based on my knowledge, this reportdoes not contain any untrue statement of a material fact or omit tostate a material fact necessary to make the statements made, in lightof the circumstances 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 present 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's othercertifying officer(s) 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: |

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|   | (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; |

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|   | (b) | designedsuch internal 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; |

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|   | (c) | evaluatedthe effectiveness 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 |

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|   | (d) | disclosed inthis report 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 |

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| 5.  | Theregistrant's other certifying officer(s) and I have disclosed,based on 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 theequivalentfunctions): |

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|   | (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 |

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|   | (b) | any fraud,whether or not material, that involves management or other employeeswho have a significant role in the registrant's internal controlover financial reporting. |

Date: March  10,2006

|  | /s/ A. E. FestaA. E.FestaPresident and Chief ExecutiveOfficer |
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