We describe spontaneous longitudinal growth in girls with Turner's syndrome (TS), using the infancy-childhood-puberty (ICP) growth model. Length/height during the first 12 years of life was studied in 58 Swedish girls with TS. Their mean length at birth was 47.8 cm (SDS -1.4) and mean height at 12.0 years of age 127.3 cm (SDS -3.0). A clear age-dependent subnormality was observed in the change in length-height SDS (delta SDS). Mean delta SDS values at ages 0.0 to 0.5 and 3.0 to 6.0 years were normal. In contrast, the mean delta SDS at ages 0.5 to 3.0 and 6.0 to 12.0 years were subnormal. The onset of the childhood growth component (normally located between 0.5 and 1.0 year of age) was, on the average, delayed by 0.28 year. This accounts for the subnormality of delta SDS at 0.5 to 3.0 years of age. About 50% of the variation in height at 12.0 years of age, as determined by a multiple linear regression analysis, was significantly explained by length at 0.5 year of age, age at the onset of the childhood component, and delta SDS at 6.0 to 12.0 years of age.