A minority of children born small for gestational age (SGA) fail to achieve sufficient catch-up growth during infancy and remain short throughout childhood, apparently without being growth hormone (GH) deficient. A previous metanalysis of four trials revealed that GH treatment over a period of 2 years induced a dose-dependent acceleration of linear growth and, to a lesser extent, of the rate of bone maturation in short, prepubertal children born SGA. The rate of bone maturation and the change in height SDS for bone age from the previous 2-year metanalysis have been re-analysed according to chronological age (two prepubertal age groups: group A, 3.0-5.9 years old; group B, 6.0-8.9 years old). The rate of bone maturation was slower in younger than in older prepubertal children; this difference was more marked in children receiving high-dose (0.2 or 0.3 IU/kg/day) GH treatment (p < or = 0.01). Accordingly, the change in height SDS for bone age was increased by high-dose GH treatment in both age groups (p < or = 0.01), and was more pronounced in younger than in older children (1.45 +/- 0.28 versus 0.63 +/- 0.20; p < or = 0.01). Height SDS data from 100 short, prepubertal children born SGA have been analysed over 4 years. The change in height SDS appeared to be related to the average dose of GH. A mean GH dose of 0.1 IU/kg/day over 4 years was administered either as 0.1 IU/kg/day for 4 years (continuous) or as 0.2 IU/kg/day for 2 years, followed by 2 years without GH treatment (discontinuous). After 4 years of treatment, the increase in height SDS for the continuous and discontinuous treatment schedules was similar, being 1.42 +/- 0.10 SDS and 1.58 +/- 0.17 SDS, respectively. In a second regimen, a mean GH dose of 0.2 IU/kg/day over 3 years was administered either as 0.2 IU/kg/day for 3 years (continuous) or as 0.3 IU/kg/day for 2 years, followed by 1 year without GH treatment (discontinuous). After 3 years, the increase in height SDS with the continuous and discontinuous treatment schedules was similar, being 2.01 +/- 0.18 SDS and 2.22 +/- 0.16 SDS, respectively. GH administration was well tolerated in all treatment groups. In conclusion, the rate of bone maturation in short, prepubertal children born SGA treated with GH appeared to depend not only on the dose of GH, but also on the age of the child. GH treatment resulted in a prolonged increase in height SDS, the magnitude of the rise being dependent on the average GH dose rather than on the continuous or discontinuous mode of GH administration.