In order to analyze the trends of hemolytic streptococcal infections, we have investigated the source of clinical specimens, monthly isolation rates, and the isolation rates by sex and age o patients of 6,440 hemolytic streptococci (group A, B, C and G) isolated from clinical specimens in hospitals in Saitama during the period of 1979-1987. 1) Serological group of 6,440 hemolytic streptococci isolated from clinical specimens were 4,691 (72.9%) isolates of group A, 1,535 (23.8%) isolates of group B, 47 (0.7%) isolates of group C, and 169 (2.6%) isolates of group G. 2) The main clinical sources of hemolytic streptococci, group A streptococci were 4,243 (90.7%) isolates from throat swabs, 117 (2.5%) isolates from ear secretions, 87 (1.9%) isolates from nose secretions, and 58 (1.2%) isolates etc., group B streptococci were 647 (42.2%) isolates from urines, 446 (29.1%) isolates from vaginal swabs, 127 (8.3%) isolates from throat swabs, 118 (7.7%) isolates from semen, 55 (3.6%) isolates from urethral secretions, 13 (0.8%) isolates from blood, and 9 (0.6%) isolates from cerebrospinal fluid etc.. 3) The monthly isolation rates of hemolytic streptococci, showed that group A streptococci had a general trend by the season, that is, the highest ratio in winter and the lowest ratio in summer, group B streptococci was not influenced by the season. 4) The isolation rates by sex of patients showed that group A streptococci had no difference between male and female, however, group B streptococci showed that the isolation rate of female was higher than that of male with the ratio of 7 to 3.(ABSTRACT TRUNCATED AT 250 WORDS)