Slipped capital femoral epiphysis is a rare complication of growth hormone therapy. We report on a young man with pituitary insufficiency, diagnosed and treated with growth hormone at the age of 14 9/12. The patient withdrew from treatment after 6 months of growth hormone therapy without significant catch-up growth or complications. At the age of 21 8/12 years slipping of the left femoral capital epiphysis became apparent 2 1/2 months after treatment with growth hormone had been resumed in combination with low dose testosterone. Young adult patients with unfused epiphyses undergoing growth hormone substitution should be informed that pain in the lower extremities during therapy may be an important sign of a complication of growth hormone therapy. In this age group, patients complaining of pain in the limb should alert the physician to the possibility that a slipped capital femoral epiphysis may be present.