Class I and II posterior composite resin (Ful-Fil) restorations were placed and were clinically evaluated, according to the US Public Health Service criteria, at baseline, 6 months, 5 years, and 8 years. At 5 years/8 years, alpha scores were assigned to the following percentages of restorations: 16%/31% for color match; 65%/62% for marginal discoloration; 74%/54% for cavosurface marginal discoloration; 100%/100% for axial contour; and 81%/65% for anatomic form. At 5 years/8 years, 56%/33% of Class II restorations had tight proximal contacts; 45%/44% had light contacts; and 0%/22% had no contacts. Transient postoperative sensitivity was reported in 6% of the restorations. Indirect evaluation indicated that there was an average of 64 +/- 35 microns of wear at baseline (because of overfinishing), 105 +/- 67 microns at 6 months, 217 +/- 76 microns at 5 years, and 253 +/- 82 microns at 8 years. At 5 years, three of the restorations, and at 8 years, four additional restorations, were clinically unacceptable because of recurrent caries and/or excessive wear. Final success rates of 90% and 77% at 5 and 8 years, respectively, were calculated.