We assessed the radiological features of the arthropathy seen in patients with calcium pyrophosphate dihydrate (CPPD) disease or pseudogout. Standard AP projections of the hands, pelvis and knees were evaluated in 74 patients with pseudogout, 68 cases of primary osteoarthritis (OA) and 78 "normal" controls matched by age and sex. A grade from 0 to 3+ was assigned to each of the 4 variables of OA: joint space narrowing, sclerosis, osteophytosis and subchondral cysts. Radiographic findings of OA were more prevalent (p less than 0.005) and severe (p less than 0.001) in the group with pseudogout than in the controls. When the groups with pseudogout and primary OA were compared, no significant differences were found in the overall severity of radiographic changes with only minor differences in its distribution. The pseudogout patients had greater changes in the metacarpophalangeal joints and a lesser involvement of the trapeziometacarpal joints. No radiological differences were observed in patients meeting McCarty's criteria for clinical types A and C.