Objective long-term clinical data are necessary to evaluate the performance of dental restorations. This prospective clinical trial evaluated composite and ceramic inlays for clinical acceptability as restorative materials in posterior teeth and provided 2-year results. The study involved 7 student operators placing 47 composite inlays (Tetric, blend-a-lux, Pertac) and 24 ceramic inlays (Empress) under the supervision of an experienced dentist. Clinical assessment of 56 inlays (78.9%) was performed after 2 years with modified USPHS criteria and statistically analyzed using the Mann-Whitney U test and Fisher's exact test. All the ceramic inlays and 90% of the composite inlays were considered clinically excellent or acceptable. During the first year 3 composite inlays failed and during the second evaluation period 1 had to be replaced. Ceramic inlays produced significantly better "anatomic form of the surface" (P = 0.038) and "integrity of the restoration" values (P = 0.043). Inlays in small cavities exhibited superior "marginal integrity" (P = 0.026) and "marginal discoloration" values (P = 0.034). Fisher's test revealed a significantly higher failure rate in molars than in bicuspids (P = 0.034). Posterior tooth-colored inlays exhibited a success rate of 100% for ceramic inlays and 90% for composite inlays even if placed by relatively inexperienced but supervised student operators.