The production of bacteriolytic enzymes by Enterobacteriaceae in various growth conditions was investigated. Peptone-based media containing killed Gram-negative cells facilitated detection of bacteriolytic enzyme production in the highest number of species. These belonged to the genera Serratia, Proteus, Morganella and Providencia. In contrast, Escherichia coli, Shigella, Salmonella, Klebsiella, Enterobacter and Citrobacter species did not produce bacteriolytic activities in any of the conditions tested.