A clinical and radiological survey of 77 members of a Tunisian family with hereditary chondrocalcinosis was performed. Articular chondrocalcinosis was documented by X-rays in 7 living members of 3 generations. No associated or secondary forms of the disease were found. Clinical features of the disease appeared early in life and radiologic involvement was extensive. The mode of inheritance appeared to be autosomal dominant with incomplete penetrance. Electron microscopy study of synovium and cartilage biopsies from one patient demonstrated calcium pyrophosphate dihydrate crystals. HLA typing revealed that all affected subjects bore the haplotype A1 B12 DR3.