Transient synovitis of the hip and Legg-Calve-Perthes (LCP) disease are the commonest causes of painful hip in young children. While the prognosis for transient synovitis is generally good, the experience with this series of patients indicates that LCP disease may be antedated by a stage of synovitis indistinguishable from transient, self-limiting synovitis. Since the prognosis for LCP disease is drastically different from that of transient synovitis, early differential diagnosis is essential. To this end closer observation of children with transient synovitis is warranted.