The rabbit muscle implantation test as described by Lawrence et al. (1972) was applied evaluate the acute non-specific toxicity of 3 amalgams and 2 composite materials, in order to test both the materials' toxicity and the suitability of the method used. The materials were implanted after different ageing times: 5 min, 1 h, 24 h and 7 days. Macroscopical as well as microscopical evaluation was performed. Biological reactions of the amalgams proved to be dependent upon the ageing time. All amalgams were strongly toxic at the 5-min and 1-h periods. By the 7-day period the high-copper two component amalgam showed a moderate reaction, the other two amalgams no or uncertain reactions. The composite materials did not show a dependency of the toxicity upon the ageing time as did the amalgams. They evoked a slight to moderate tissue reaction. The results obtained in this study are in accordance with clinical experience. We regard the rabbit muscle implantation test as a suitable method for screening the chemically initiated toxicity of solid materials.