Thirteen pedigrees with familial articular chondrocalcinosis were identified through a systematic radiologic survey of the first-degree blood relatives of 76 patients with chondrocalcinosis. Forty-one persons, 30 women and 11 men, distributed in 25 sibships were affected. Their mean age at the time of study was 65.09 +/- 11.36 years. The disease was of early onset only in four pedigrees. The clinical manifestations in these four pedigrees were similar to those found in the kindred with a late onset. In 15 persons, the process was asymptomatic. In the 26 symptomatic patients, the arthropathy was mild, with clinical and radiologic features similar to those observed in sporadic chondrocalcinosis. There was no linkage of chondrocalcinosis to the HLA-A and HLA-B antigens in the 11 pedigrees in which tissue typing was performed. The pattern of involvement in these 13 pedigrees supports an autosomal dominant mode of inheritance. These data suggest that hereditary chondrocalcinosis is not infrequent and very often is clinically indistinguishable from the sporadic form of the disease.