English Abstract At two rendering plants for dead animals and animal wastes in the Netherlands studies were carried out in 1992 on the efficacy of autoclaving processes and the microbiological condition of processing halls and final products. At plants A and B spores of sulfite reducing clostridia were detected in 3,3% and 11,5% respectively of the samples taken directly after autoclaving. In one sample, from plant A, spores of C.perfringens were concerned. In samples of final product Salmonella was not detected. In all but one of these samples the Enterobacteriaceae-count was less than 10 cfu per gram. At plants A and B Salmonella was detected in 36,7% and 3,7% respectively of samples of dust taken from the processing halls. In 30,0% of samples of dust from plant A the Enterobacteriaceae-count exceeded 300 cfu per gram.