A family study of a patient with chondrocalcinosis (pseudogout syndrome) revealed characteristic abnormal joint calcifications and a clinical picture suggestive of pseudogout in two siblings, while less specific calcifications were noted in a third sibling and two daughters. Numerous crystals consistent with calcium pyrophosphate dihydrate were seen on synovial fluid analysis and x-ray studies demonstrated widespread calcification of articular hyaline and fibrocartilage. No gross defect in calcium or phosphorus metabolism was detected by metabolic balance and radioactive calcium kinetic studies. Uptake of isotope in the synovial fluid paralleled that seen in other extracellular fluid compartments, reaching equilibrium with serum within six hours. Colchicine appeared to be of value in ameliorating the symptoms of an acute attack. The findings noted in this study support the concept that this syndrome may be hereditary.