Swiss cheese was manufactured with single strains of Propionibacterium shermanii and Propionibacterium arabinosum. These strains grew well and poorly, respectively, at 7.2C, a temperature at which Swiss cheese is often stored commercially. Cheese made with the P. shermanii strain showed a much greater tendency to split and had a larger eye volume than cheese made with P. arabinosum. It was not possible to relate the greater tendency to splitting with greater gas production or proteolysis by the P. shermanii.