In a survey-study of all living Dutch patients with cystic fibrosis (CF) born before 1971 data have been gathered on sex, age, age at diagnosis; height and weight; treatment and social development. The group consists of 102 schoolchildren (8-11 years), 179 adolescents (12-21 years) and 28 young adults (22-40 years). Males are in the majority, especially in the 12 to 17 age group (61%). In 51% of all patients CF was diagnosed before the age of 2, and in 75% before the age of 5. Male CF patients are on average 6 cm (0.84 SD) shorter than normal and female patients 3 cm (0.48 SD). As far as weight for height is concerned, 54% of the CF patients fall below the 10th percentile. Weight for height is slightly lower in females than in males. CF patients usually leave primary school at an older age than their healthy peers. In comparison to healthy adolescents of the same age, adolescents with CF attend full-time day-school for a longer time, more of them receive general education and fewer take vocational training. Adolescents and young adults with CF do not stay longer than normal in the protective environment of their parental home.