The primary goal of this study was to determine if the ability to undergo catch-up growth following a transient injury is preserved in an experimental model of moderate chronic renal failure (CRF) and the effect of growth hormone (GH) administration on such phenomenon. Young rats were subtotally nephrectomized (days 0 and 4) (Nx). From days 11 to 13, food intake was restricted in subgroups of Nx and control (C) rats (NxR and CR). After refeeding, subgroups of NxR and CR rats received GH from days 14 to 20 (NxRGH and CRGH). Rats were killed on days 14 (C, CR, Nx, NxR), 17 and 21 (C, CR, CRGH, Nx, NxR, NxRGH), and 36 (C, CR, Nx, NxR). Longitudinal growth rate was measured by osseous front advance in the proximal tibiae. With refeeding, growth rate of CR, NxR, and NXrGH rats became significantly greater than that of C, indicating catch-up growth. This occurred later and with lower growth rate in NxR than in CR rats, whereas the characteristics of catch-up growth in CR and NxRGH animals were similar. Changes in growth rate were associated with modifications in the morphology and proliferative activity of growth cartilage. We conclude that catch-up growth occurs in renal insufficiency but follows a different pattern from that observed with normal renal function. GH treatment normalizes the pattern of catch-up growth in CRF. Changes in growth velocity are associated to modifications in the structure and dynamics of growth cartilage.