Two hundred and twenty-seven individuals followed up from birth for 5 to 34 years were analyzed for incidence of "mild" and "more severe" respiratory tract infections. Group data were compared with those of other studies. Records showed consistent patterns for individual subjects through growth. Individuals born between 1930 and 1945 and those born between 1946 and 1962 were similar in frequency of infections. Similarity of incidence of respiratory infections in family groups was found. Tonsillectomy and adenoidectomy (T and A) was associated with a slightly higher than average incidence of "mild" respiratory tract infections, but surgery was more closely linked with bursts of frequent "more severe" infection in girls. In both sexes there was a statistically significant decrease in "more severe" respiratory tract infections following T and A. The proportion of the group in whom T and A was performed remained constant through the 32 years.