Calcium pantothenate and pantethine were investigated for influence on the estrouscycle and reproductive performance in mice deficient in pantothenic acid. Female miceof the dd N strain, 40 days of age, were placed on control diets (CLF, A, CA-1) for 21days. Only those which had exhibited at least 2 regular cycles of 4, 5, or 6 days eachduring this period were used (Table 2). As shown in Fig. l, they were divided iutto5 groups.I) The estrous cycle and diestrous stage per cycle were prolonged by feeding ondiets deficient in pantothenic acid for 70 days (Table 5).2) There was a tendency to decrease in implantation and increase in incidenceof fetal mortality among mice given CLEA diets deficient in pantothenic acid forthree weeks (Table 6).3) The decline in sexual function caused by feeding on a pantothenic aciddeficient diet was improved by subcutaneously injection with calcium pantothenatcrand pantethine (Tables 5 and 6).