Changes in the prevalence of tonsillectomy and circumcision in eleven year olds are described in two birth cohorts spaced 12 years apart. Both types of operation were less prevalent in the later (1958) cohort; tonsillectomy fell by a fifth and circumcision by more than half. These falls were confined to tonsillectomy before the age of six and circumcision under one year. Social class differences in tonsillectomy were found in both cohort studies but the strong social class gradient in circumcision reported in the 1946 cohort had vanished in the 1958. Regional and birth rank differences are found for both types of operation; these show substantial changes over time. These results are discussed in the context of changing professional opinions about the worth of these operations.