BACKGROUND: Existing evidence on profiles of psychological distress across adulthood uses cross-sectional or longitudinal studies with short observation periods. The objective of this research was to study the profile of psychological distress within the same individuals from early adulthood to early old age across three British birth cohorts. METHODS: We used data from three British birth cohorts: born in 1946 (n = 3093), 1958 (n = 13 250) and 1970 (n = 12 019). The profile of psychological distress - expressed both as probability of being a clinical case or a count of symptoms based on comparable items within and across cohorts - was modelled using the multilevel regression framework. RESULTS: In both 1958 and 1970 cohorts, there was an initial drop in the probability of being a case between ages 23-26 and 33-34. Subsequently, the predicted probability of being a case increased from 12.5% at age 36 to 19.5% at age 53 in the 1946 cohort; from 8.0% at age 33 to 13.7% at age 42 in the 1958 cohort and from 15.7% at age 34 to 19.7% at age 42 in the 1970 cohort. In the 1946 cohort, there was a drop in the probability of caseness between ages 60-64 and 69 (19.5% v. 15.2%). Consistent results were obtained with the continuous version of the outcome. CONCLUSIONS: Across three post-war British birth cohorts midlife appears to be a particularly vulnerable phase for experiencing psychological distress. Understanding the reasons for this will be important for the prevention and management of mental health problems.