The auxological characteristics and the response to growth hormone (GH) treatment of children with idiopathic short stature were studied, using the database of the Kabi Pharmacia International Growth Study. Pretreatment data from a total of 271 children were analysed. The children were selected for a birth weight above -2 SDS. The correlation coefficient of birth weight SDS and birth length SDS was 0.51, compared with 0.72 for the reference population. Median length at birth was -0.6 SDS, which fell to -2.5 SDS by 3 years of age. Thereafter, there was no further loss in height SDS. The response to GH treatment was studied in 222 of these prepubertal children who were given six or seven injections/week over a 3-year period. During this time, the median height SDS increased from -2.5 to -1.5, with those children receiving more than 0.65 IU/kg/week having a greater gain in height SDS than those on 0.5 IU/kg/week or less. The degree of bone age delay did not appear to influence the response to GH therapy.