To assess the radiological features of hereditary articular chondrocalcinosis, we performed a blind comparative study between 21 randomly selected patients with hereditary disease and 21 cases of sporadic pseudogout matched for age and sex. Each individual had AP projections of the hands, pelvis and knees. The films were evaluated for the presence of articular chondrocalcinosis and for the severity of the associated degenerative arthropathy. A grade of 0 to 3+ was assigned to each of the 4 variables of osteoarthritis: joint space narrowing, sclerosis, osteophytosis and subchondral cysts. The mean number of joints with chondrocalcinosis and its distribution was similar in both groups. In addition, no differences were found in the overall severity of the associated degenerative arthropathy. In both groups the disease was characterized by oligoarticular calcification and a mild degenerative arthropathy. These data along with data from other reported pedigrees, show that the radiological appearance in the hereditary type is frequently indistinguishable from that commonly observed in sporadic articular chondrocalcinosis.