As part of an ongoing international multicentre study, 19 children (14 girls, 5 boys) with central precocious puberty (CPP) were treated with a slow-release gonadotrophin-releasing hormone (GnRH) agonist, triptorelin, for 4 years. After 3 years of treatment, height velocity stabilized at 4.0 cm/year. Predicted adult height (mean +/- SD) increased from 158.9 +/- 6.8 to 164.9 +/- 6.6 cm in girls (n = 14, p less than 0.01), and from 174.4 +/- 18.5 to 184.3 +/- 17.1 cm in boys (n = 4, p less than 0.05). In 12 additional girls who had started the multicentre study but discontinued triptorelin treatment after 2.2 +/- 0.5 years, menses started 9.8 +/- 3.7 months after cessation of treatment in all but one patient. Height velocity increased over the first 6 months after discontinuation of treatment, from 3.6 +/- 0.1 to 5.4 +/- 2.5 cm/year, and remained higher than pretreatment values in the second 6 months, but decreased subsequently. Bone maturation increased, and no significant improvement in predicted adult height was observed. For auxological reasons, therefore, it may be advisable to continue triptorelin treatment for as long as possible. Concomitant growth hormone (GH) therapy was initiated in three girls with CPP with height velocities of 3.2-3.6 cm/year after 3 years of treatment with triptorelin and predicted adult heights of less than the third centile for Dutch girls. Prior to the administration of GH, all patients had subnormal 24-hour GH profiles and GH responses to arginine provocation. GH treatment increased height velocity markedly in all girls, and improved predicted adult height.(ABSTRACT TRUNCATED AT 250 WORDS)