There are few published studies on the genetics of body growth to maturity in sheep. Such information is required for choosing an optimal time of selection for body weight and to predict correlated responses to selection at all stages of an animal's lifetime. The data were derived from a randomly selected control flock of Scottish Blackface sheep on a hard heather hill research farm in Peeblesshire, Scotland. The objectives of the analysis were to estimate the heritability of body weight at various ages between birth and maturity, and the genetic correlations between these weights.