This work concerns the effect of age and the diabetic gene(s) on the growth capacity of skin fibroblasts in culture. Cells from normal subjects and the progeny of conjugal diabetics have similar lifespans after multiple passages in mass culture VSports手机版. The combined lifespans in vitro are inversely proportional to the age of the donor. When individual cells are plated, more of those from normal subjects are able to form colonies. The difference in plating efficiency is apparent when first tested after 20 generations of growth, persists at 30 and 40 generations, but disappears after 50 generations. This cell culture system should be useful in studying the inheritance of the diabetic gene(s), the pathogenesis of the diabetic state, and the relationship between aging and diabetes, both of which decrease plating efficiency. .