Purpose: The purpose of this in vivo study was to evaluate the marginal fit of inlay and crown abutments for fixed partial dentures (FPD) made from a new all-ceramic material. Materials and Methods: Sixteen patients were selected for the study. After abutment preparation, impressions were made and master dies were fabricated. FPDs were made with the experimental heat-pressed lithium-disilicate glass-ceramic following the manufacturer’s recommendations. At random, one abutment of each FPD was chosen for evaluation (11 crown and 8 inlay abutments). Impressions of the restoration margins were taken before and after adhesive cementation. Replicas of the abutment margins were investigated by SEM. The marginal discrepancies were evaluated in sections of 200 µm. The highest value of each section was applied, and the mean of all sections of each replica was used for statistical analysis. Results: The median of the marginal discrepancies before cementation was 96 µm for crowns and 89 µm for inlays. After adhesive cementation, the median increased for crowns to 130 µm and for inlays to 92 µm, a significant increase in the marginal discrepancies caused by cementation for crowns, but not for inlays. There were no significant differences between the discrepancies of crowns and inlays before or after cementation. Conclusion: The maximum marginal discrepancies found in this study were between 50 and 265 µm before cementation and between 70 and 285 µm after cementation, with no significant differences between the means for crowns and inlays. Adhesive cementation caused a significant increase of the marginal discrepancies for crown, but not inlay, abutments. Int J Prosthodont 2003;16:587–592.