In connection with osteosynthesis carried out on the tibias of rats we compared acrylic and bis-GMA plastics (CMW and Silar) and acrylic emulsion and acrylic dispersion used as intermediary material. A total of 80 rats of both sexes were used. The rats were divided into four groups, in which different intermediary material combinations were tested. The observation times were 1, 3, 6, 12, and 24 weeks. Macroscopical, radiological, histological, oxytetracycline fluorescence, and scanning electron-microscopical studies were done. Histologically, the Silar proved to be the more reliable fixation material and acrylic dispersion the better intermediary material. Furthermore, the radiological results were better (P less than 0.05) when acrylic dispersion was used as the intermediary material and Silar as the plastic.