The effect of growth hormones (GH) on renal growth was measured in growing uremic rats using a five-sixths nephrectomy model and GH, 5 mg/kg per day. At the end of 8 weeks, somatic size was significantly smaller in the untreated uremic rats. The uremic rats given GH were the same size as the non-uremic control animals. Organ size (heart, liver and kidney) differed in that only untreated uremic animals had a significantly smaller kidney weight. Despite a five-sixths nephrectomy, the uremic animals receiving GH had kidneys the same size as sham-operated control animals. Renal function was not changed by GH therapy in either control or uremic animals. DNA content expressed as milligrams per kilogram kidney tissue was low only in the untreated uremic rats. Glomerular volume and proximal tubular area were elevated in both groups of uremic animals but were elevated to a significantly greater degree in those receiving GH. GH given in large doses to growing animals appears to induce both somatic and renal growth.