A three-year clinical study was completed at the College of Dentistry comparing the overall performance of Class I amalgam restorations with preventive resin restorations (PRRs). Seventy-four PRRs and fifty-two amalgam restorations were placed in the posterior teeth of thirty-eight patients. The PRR was composed of two materials: P-50 (3M Corp.), a heavily filled composite resin, and White Sealant (3M Corp.), a light-cured sealant. Fast-set Dispersalloy (Johnson and Johnson Corp.) was used for the amalgam restorations. The restorations were evaluated at six months, one year, two years and three years. The USPHS/Ryge system was used to evaluate anatomic form, marginal adaptation, marginal discoloration and recurrent caries of both type restorations. A restoration was considered a failure if any part of the restoration was replaced due to secondary caries. There were two failures of PRRs at six months, and four failures at one year. Failures were due to non retention of the sealant of the PRR and possibly related to operator error. The failures were easily repaired and removed from the study. No PRR failed at the two or three year evaluations. No amalgam restoration failed within the three year period.