The aim of this study was to study the secular changes in anthropometric data over calendar time in patients with cystic fibrosis (CF). Growth curves were constructed for 270 patients based on height and weight registrations from the medical files. Height, body mass index (BMI), magnitude of pubertal peak height velocity (PHV) and age at PHV were analysed for possible secular changes from the 1960s to the 1990s. There was a significant change in height over calendar time in only 1 of 12 age groups. BMI showed a significant increase in 10- and 15-y-old boys and girls and in 5-y-old girls. The magnitude of PHV changed significantly over time, whereas age at PHV was constant. No significant changes in height and age at PHV over calendar time were observed; this was probably due to a selection bias since the oldest patients, who survived to be part of the present investigation, represented milder forms of the disease. The increase in BMI and change in magnitude of PHV over calendar time may reflect the improvement in treatment leading to a better survival and clinical status through puberty. The increase in BMI and change in magnitude of PHV were sufficient to overcome the selection bias from older patients with milder disease.