EXHIBIT31(i).1

CERTIFICATION OF PERIODIC REPORT UNDER SECTION 302OF THE SARBANES-OXLEY ACT OF 2002

I, A. E. Festa,certifythat:

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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 onmy knowledge, this report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make thestatements made, in light of the circumstances under which suchstatements were made, not misleading with respect to the period coveredby thisreport; |

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|   | 3. | Basedon my knowledge, the financial statements, and other financialinformation included in this report, fairly present in all materialrespects the financial condition, results of operations and cash flowsof the registrant as of, and for, the periods presented in thisreport; |

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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) | designedsuch disclosure controls and procedures, or caused such disclosurecontrols and procedures to be designed under our supervision, to ensurethat material 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) | disclosedin this report any change in the registrant's internal controlover financial reporting that occurred during the registrant'smost recent fiscal quarter (the registrant's fourth fiscalquarter in the case of an annual report) that has materially affected,or is reasonably likely to materially affect, the registrant'sinternal control 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) | anyfraud, whether or not material, that involves management or otheremployees who have a significant role in the registrant'sinternal control over financial reporting. |

Date:November 4, 2005

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