The linear growth of Swedish children with cystic fibrosis (CF), is described using the infancy-childhood-puberty (ICP) growth model. Length/height was studied in 51 patients during their first 8 years of life. The median age at diagnosis was 0.4 years (range 0.0-6.1 years). At birth, their mean length was close to normal, but the gain in length over the first 0.25 years of life was significantly below normal, resulting in a mean length SDS of -1.3. Length remained subnormal up to 1.0 year of age. Thereafter, catch-up growth occurred, resulting in almost normal height (mean SDS-0.3) at 5.0 years of age. Between 5.0 and 8.0 years of age growth was normal. The mean age at onset of the childhood component was not significantly different from the controls. Hence, the catch-up growth did not occur until after the onset of the childhood component. This study shows that the postnatal linear growth rate is retarded in children with CF during the first months of life. This is almost completely compensated for by a supranormal growth rate that starts at the end of the first year of life.