Streptococcal infections of pigs were found in 36 (24.8%) of 145 samples from diseased pigs byhistopathological and bacteriological examinations in Shimane Prefecture over a period from 1979to 1981.Serological groups Of 33 streptococcal strains, 20 (60.6%) belonged to Lancefield group R and12 (36.4%), to C but one was unidentified.The disease seemed to occur most commonly in litter piglets associated with weaning, moving andmixing. Morbidity ranged from 4.2 to 81.8% in infected herds.Principal diagnostic signs of group R infections were nervous symptoms with meningitis, pyrexiaand leucocytosis. Those of group C infections were hemorrhage in visceral organs and pyrexia.Group R strains were most frequently (94.1%) isolated from the brain and group C strains from mainvisceral organs at a similar rate. The former were highly sensitive to penicillin and the latter topractically all antibiotics, except macrolides.