Slipped capital femoral epiphyses are rarely associated with primary hyperparathyroidism, and only four cases have been documented in the English literature. We report such a case. A 13-year-old boy presented with bilateral slipped capital femoral epiphyses. Investigation showed that he had primary hyperparathyroidism due to a parathyroid adenoma. The adenoma was removed, and then the epiphyses were pinned in situ 3 weeks later. The pins were removed 3 months postoperatively when the physes had closed. The patient had a painless hip 1 year later at follow-up. We concluded that identification and excision of the hyperparathyroid adenoma and in situ pinning of the slipped epiphyses results in satisfactory treatment of the condition.