Incidence and prevalence of hemolytic and group A streptococci were determined for 3,479 school children in Nashville, Tennessee from 1953-1954 through 1973-1974 inclusive. Of 53,827 throat cultures, 17.98% were positive for hemolytic streptococci and 12.87% for group A; 26.19% group A strains were typable. Types 6, 1, 12, 4, 5, and 3 were the most frequently isolated. Percentages of children with at least one positive culture for both hemolytic (H) and group A streptococci (A) were highest in 1953-1954 (H--79.3%, A--71.0%); 1963-1964 (H--83.5%, A--74.6%); 1969-1970 (H--74.6%, A--65.0%); and 1973-1974 (H--83.1%, A--71.1%) and highest by month in February, declining erratically until the summer. Some children acquired type-specific antibodies in the absence of streptococcal disease. There was a significant increase in positivity rates for hemolytic and group A streptococci from ages 5 to 7 through age groups 6 to 8 and 7 to 9 and a slow decline in the older age groups. Race did not appear to be an important factor in determining positivity rates; rates were significantly higher among children from low socioeconomic areas regardless of whether they were black or white.