Primary synovial osteochondromatosis is a disorder characterized by the formation of multiple intra-articular osteocartilaginous bodies. Clinical symptoms are not specific, which makes the diagnosis difficult. Magnetic resonance imaging is useful in the diagnosis of synovial osteochondromatosis of the hip, especially in cases in which ossified bodies are not present. Synovial osteochondromatosis tends to be progressive but self-limiting and the optional treatment is controversial. We described two patients with primary osteochondromatosis of hip who presented with symptoms and signs of single joint arthropathy of hip. (J Korean Acad Rehab Med 2004; 28: 627-630)