The results of this study (1969–1971) confirm previous findings that incidence rates for hemolytic and group A streptococci in Nashville school children fluctuate sporadically. During these two years, there was a significant decrease in streptococcal incidence and in typability of group A streptococci. A positive throat culture was not associated significantly more often with symptoms of an infection of the upper respiratory tract than when symptoms were absent. The larger the number of group A streptococci present in the throat culture, the more likely was a streptococcal antibody increase to occur. Nevertheless, some children with small numbers of group A streptococci had an antibody increase, and the degree of positivity of the throat culture was not a very accurate indication of whether an antibody response would occur. Epidemiologic factors such as age, sex, race, or crowding in the home did not seem to play a highly significant role in rates. Seasonal influences were marked in 1969–1970 but not in 1970–1971. Regarding socioeconomic background, the rates were consistently lower in Clemons school, which serves a predominantly black neighborhood of higher socioeconomic level, than in the other two schools. Our findings confirm that the incidence of acquisition of the hemolytic streptococcus is a continually changing, dynamic process among school children.