Sixty white female BALB/c mice at age 6 weeks were divided into two groups: Hydrogenated cotton seed oil and control. Each group was divided into three subgoups: 6, 9 and 12 weeks. The first group was fed with diet containing 10% hydrogenated cotton seed oil for 3 weeks, but controls with oidinary diet, ad libitum. Biopsy and histological studies showed decrease in nianber of follicles, but increase of atretic bodies. This was higher in 6 and 9 weeks. Decrease was more for primary follicles. The above phenomenon could be due to saturation of linoleic acid contained. in hydrogenated cotton seed oil.