Pigmented villonodular synovitis is a destructive, fibrohistiocytic proliferation producing innumerable villous and nodular synovial protrusions. Its common locations are knee, ankle, foot, and hip. Although histologic feature of this tumor is well known, there have been few reports on the fine needle aspiration cytology findings. We report the cytologic features of a biopsy-proven case oi pigmented villonodular synovitis. The patient was a 21-year-old male with a mass of the right knee for 2 years. On fine needle aspiration cytology, the aspirates was composed of abundant mononuclear histiocytic cells, singly and in clusters, multinucleated slant cells, and hemoslderin pigments.