Summary The influence of the cultivation temperature on growth and production of extracellular proteins was examined for the group C streptococcus S. equisimilis, strain H 46 A. The temperature range studied was from 28°C to 43°C. The analytical methods used included the determination of enzyme activities, isoelectric focusing and crossed Immunoelectrophoresis. The strain was able to grow in the entire temperature range with maximum growth at 28°C. The amounts of extracellular proteins elaborated depended on both the cultivation temperature and the biomass production. The specific temperature for optimal production of certain enzymes were determined. The majority of these was produced at optimal rate at a temperature of 28°C. Besides isoelectric focusing and crossed Immunoelectrophoresis showed that additional proteins exist, the production of which was reduced at low temperatures. Isoelectric focusing revealed that in a temperature range from 28°C to 37°C approximately 28 different extracellular proteins were produced. In the same temperature range the presence of about 30 antigens was demonstrated by crossed immunoelectrophoresis.