Many children with chronic renal failure (CRF) present with a reduced height and a reduced height velocity resulting in diminished final height irrespective of renal replacement therapy. Recombinant human growth hormone (rhGH) has become a new treatment modality for short renal patients, and the response to rhGH varies widely. In order to identify possible predictors of response to rhGH, the influence of sex, chronological age, bone age, pubertal status, height and height velocity at basal, target height, treatment modality for CRF, residual glomerular filtration rate (GFR), and steroid treatment was analyzed by single and multiple regression analysis in 49 children prior to and after renal transplantation. During the first treatment year with 28 to 30 IU rhGH/m2/week given by daily s.c. injections, height velocity was highest in patients on conservative treatment and lowest in patients on dialysis. Height velocity expressed in cm/year was inversely correlated with age (r = -0.63; P < 0.0001) and positively correlated with pretreatment height velocity (r = 0.65; P < 0.0001). The increment in height velocity SDS (chronological age) was significantly negatively correlated with the pretreatment height velocity SDS (chronological age) (r = -0.58, P < 0.001), indicating that at any given age the slowest growing children tended to respond best to rhGH treatment. It is concluded that the response to rhGH is significantly influenced by age, pretreatment height velocity, and treatment modality for CRF, whereas the influence of other variables is less important.