To shed more light on the involvement of bacterial proteolysis and lipolysis in the solubilization of dead organisms in Uranouchi Bay, a total of 300 bacterial strains were isolated from the suspended matter, newly-formed deposits, and bottom muds which were taken as samples from the bay. Proteolysis and lipolysis rates were determined under defined conditions. There were appreciable differences among bacterial levels of proteolysis and lipolysis. The in situ proteolysis and lipolysis seem to be controlled largely by strongly proteolytic and lipolytic bacteria. Higher percentages of strongly proteolytic and lipolytic bacteria were observed among isolates from suspended matter. Therefore, a large part of the bacterial proteolysis and lipolysis in decomposing organisms seemed to occur during their deposition or in the early stage after deposition onto the bottom mud. Most of the isolates which had strongly proteolytic and lipolytic activities were members of the genera Vibrio and Acinetobacter.