Two patients, aged 5 and 12 years, with Silver-Russell type dwarfism are presented. As shown by standard tests and examination of the spontaneous nocturnal hGH secretion, there was only mild regulative hGH deficiency. HGH treatment was started with daily subcutaneous injections at age 5.5 years (height 90.3 cm, -6.1 SDS, bone age 2.75 years) and 12.6 years (height 125.7 cm, -3.7 SDS, bone age 8.75 years), respectively. Treatment was monitored by serial somatomedin-C (SM-C) determinations and by knemometry (lower leg measurement). SM-C values increased in both patients by 10.5 and 4.8 fold, respectively, and remained above the prepubertal range (greater than 2.5 U/ml) during the treatment periods of 1.5 years. Pretreatment knemometric growth rate was high (after a somatomedin generation test) in patient 1 (0.7 mm/week) and low in patient 2 (0.31 mm/week). It remained at the same level in patient 1 (0.67 mm/week) and increased markedly in patient 2 (0.46 mm/week). During a treatment interruption, in both patients, knemometric growth rates fell to 0.33 and 0.30 mm/week, respectively. After resumption of treatment, now with biosynthetic hGH, growth rates increased again in patients 1 and 2 to 0.64 and 0.48 mm/week, respectively. This lower leg growth pattern was parallelled by similar changes in total body growth velocity. Even after the relatively short treatment period of 14 to 16 months, a slight net gain in statural height could be observed, as standard deviation scores for bone age increased.