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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.  | I havereviewed this quarterly report on Form 10-Q of W. R. Grace &Co.; |

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|  | 2.  | Based on my knowledge, this report doesnot contain any untrue statement of a material fact or omit to state amaterial fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleadingwith respect to the period covered by thisreport; |

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|  | 3.  | Based on my knowledge, the financialstatements, 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 registrant as of, and for,the periods presented in this report; |

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|  | 4.  | Theregistrant's other certifying officer(s) and I are responsiblefor establishing and maintaining disclosure controls and procedures (asdefined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internalcontrol over financial reporting (as defined in Exchange Act Rules13a-15(f) and 15d-15(f)) for the registrant andhave: |

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|  | (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; |

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|  | (b)  | designed such internalcontrol over financial reporting, or caused such internal control overfinancial reporting to be designed under our supervision, to providereasonable assurance regarding the reliability of financial reportingand the preparation of financial statements for external purposes inaccordance with generally accepted accountingprinciples; |

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|  | (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 |

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|  | (d)  | disclosed in this report anychange 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 |

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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 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, thatinvolves management or other employees who have a significant role inthe registrant's internal control over financialreporting. |

Date: May  9,  2006

|  | /s/ A. E.Festa                    A. E. FestaPresidentandChief Executive Officer |
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