The prevalence of chondrocalcinosis was studied in 574 hospital and clinic patients aged 50 or older who had undergone x-ray examination of the knee. Chondrocalcinosis was found in 9.6 percent of all these patients, in 5 percent of the 50-64 age group, and in 14.6 percent of the 65-94 age group. The prevalence of knee chondrocalcinosis increased in stepwise fashion between the ages of 65 and 80. A review of the literature and of the data on our few patients over the age of 80 suggests the existence of an even higher prevalence among persons of this advanced age group.