We analysed the body growth of 121 prepubertal children with polycystic kidney disease participating in a longitudinal multicentre study. The patients were followed from an age of 1 to 9 years in girls and 1 to 10 years in boys over a mean period of 3.6 years. Children with end-stage renal disease were excluded. Fifty-four patients had the autosomal dominant form of the disease and 67 the autosomal recessive form. At last observation, 2% of patients with the dominant form and 28% of those with the recessive form had an estimated glomerular filtration rate of < 60 ml/(min 1.73 m2). At first observation, the mean height SD score (SDS) in patients with the dominant form was almost the same as in controls, whilst in those with the recessive form it was significantly decreased (girls -0.82 SDS, boys -0.68 SDS, p < 0.001). During the follow-up the height SDS decreased slightly in both groups (NS). In patients with autosomal recessive kidney disease the degree of growth retardation appeared to be related to renal function: at last observation the height of girls with an estimated glomerular filtration rate of < 60 ml/(min 1.73 m2) was more retarded than that of boys (mean -2.1 SDS versus -1.5 SDS, NS). The height SDS and renal function at last observation correlated in girls (r = 0.83, p < 0.001) but not in boys (r = 0.55) with the recessive form. No correlation was found between the height SDS and hypertension. The weight-for-height SDS at onset was significantly reduced in patients with the recessive form with decreased renal function. Our data suggest that the autosomal recessive, but not the dominant, form of polycystic kidney disease is associated with early growth retardation, which seems to be more severe in girls, probably due to the more rapid deterioration of renal function.