The aim of this report was to study the rate of contrast enhancement at MRI in pigmented villonodular synovitis (PVNS). Dynamic MRI was performed in a patient with PVNS just before and 1 week and 3 years following synovectomy of the knee. As opposed to patients with rheumatic disease the patient with PVNS showed a slower enhancement rate before synovectomy than 1 week after. At 3 years follow-up the patient with PVNS showed an enhancement rate just above that of the normal controls. The results indicate that PVNS has features more common to hyperplastic or neoplastic lesions than to inflammatory ones. The results at 3 years follow-up also suggest that dynamic MRI may indicate the efficacy of arthroscopic synovectomy.