Effect of dietary levels of vitamin A (retinol) on the incidence of early lesions of the reproductive tract and ovulation in mink. Mink were fed either a control diet containing 9.4 IU/kg vitamin A or diets containing 4, 9, and 18 IU vitamin A/kg for 2.7 months. All vitamin-A-deficient mink were in poor condition. Serum vitamin A concentrations were depressed below 10 micrograms/dl in 6 weeks in deficient animals but not in the mink fed 9 or 18 IU/kg for 2 months. Two to 3 weeks after onset of the deficiency, serum vitamin A fell to 1 to 5 micrograms/dl in deficient mink. Ovulation occurred earlier in mink fed 18 IU/kg than in mink fed 9 IU/kg, although the length of the estrous cycle was shorter in animals fed 9 IU/kg. Supplementing diets containing 9 IU/kg with added retinol restored serum retinol to values in excess of 40 micrograms/dl within 3 weeks and increased ovulation rate and ovarian weight in the deficient group but did not affect body weight. Supplementing diets containing 18 IU/kg retinol for the same period did not raise serum retinol to the same levels as 9 IU/kg but increased body weight. Supplementing diets containing 9 IU/kg with 8% linoleic acid restored serum retinol to values in excess of 40 micrograms/dl within 3 weeks, and increased ovary weight and ovulation rate. Body weight and length of the estrous cycle were also increased. Low body weight due to deficient vitamin A nutrition may affect maintenance of serum retinol concentrations and thereby lead to early lesions of the reproductive tract in mink. An imbalance between retinol and linoleic acid intake appears to be a factor that leads to early lesions of the reproductive tract in mink.