OBJECTIVE--To determine whether common conditions in early childhood, such as asthma and psychosocial illness (mainly enuresis), affect height during later childhood and in adult life. DESIGN--Longitudinal follow up of subjects in the 1958 British Birth Cohort Study. Data from the birth survey and ages 7, 11, 16, and 23 were used. SUBJECTS--12,537 subjects remaining in the study at age 23, representing 76% of the target population, cohort members still alive and resident in Britain. RESULTS--Heights of children with allergic, acute or psychosomatic illness, or asthma/wheezy bronchitis did not differ by age 7 from those of children without such illnesses. When asthma was graded by severity, there was a trend (not significant) for the severe group to be shorter at ages 16 and 23. Although children with a chronic illness by age 7 were on average almost 0.5 cm shorter than children without such illnesses, this difference was reduced by half and was not significant after adjusting for maternal height, birth weight, parity, and social class at birth. However, a marked and long lasting effect was found for children with psychosocial illness who at age 7 were significantly shorter, by a mean of 0.77 cm. Within this group, enuretic children with a problem at age 11 were more than 1 cm shorter in adulthood, even allowing for other height related factors. CONCLUSIONS--Common childhood illnesses do not appear to affect height, either in the short or in the long term, although exceptions include chronic illness and enuresis. The value of height as an indicator of child health status in an industrialised country such as Britain requires further reassessment.