A new radiopaque composite resin restorative material was tested for biologic compatibility, clinical performance, and micromorphologic characteristics. Application of the test material to the dental pulp of rat incisors did not result in any toxic reaction, even when the pulp was covered by only a thin layer of dentin. A 3-year clinical test of the material in humans led to acceptable results in Class I, III, IV, and V cavities. On average, only 10% of the restorations had to be replaced within the test period (Class V restorations had to be replaced at a rate of 15%). The micromorphologic observations confirmed the clinical acceptability of the material, despite progressive changes in the surface substance and marginal conditions.