The incidence, distribution, and progression of arterial calcification in severe chronic renal disease were studied from 364 skeletal survey examinations in 152 patients (ages 15-60). The incidence increased from 30% in the 15-30 age group to 50% in the 40-50 group. The earliest and commonest site of calcification was the ankles, followed in frequency by the abdominal aorta, feet, pelvis, and hands and wrists. Progression occurred in 36% of the nondialyzed, 19% of the peritoneally dialyzed, 13% of the post-transplant, and 8% of the hemodialyzed patients.