The aims of this national multicentre study in Finland were to evaluate whether the height velocity of patients with Turner syndrome would increase with the conventional human growth hormone (GH) therapy regimen normally given to GH-deficient children and whether girls with Turner syndrome actually show GH neurosecretory dysfunction. Finally, the study should show whether GH therapy improves height prognosis and, eventually, final height. Twenty-five girls with Turner syndrome, aged 7.5-14.4 years, entered the study. Their ability to secrete GH was determined and, surprisingly, several would have been classified as having GH deficiency. All girls received GH, 0.1 IU/kg/day (maximum dose 4 IU/day) s.c., and once over 12.5 years old, they also received oestradiol valerate and fluoxymesterone. They showed a convincing increase in height velocity, and rapid growth continued during the second year of therapy. The effect of GH therapy on final height is still unknown. The therapy was remarkably free of side-effects.