The influences of dose of clomiphene and age at clomiphene treatment in prepubertal female rats on development of anovulatory sterility and pyosalpinx were investigated. By varying the amount of clomiphene administered, it was found that 50 micrograms is the minimal dose of clomiphene which will produce anovulatory sterility and pyosalpinx in a majority of female rats treated at 5 days of age. By varying the age of rats at clomiphene treatment, it was observed that the period of clomiphene sensitivity in female rats is within the first 10 days of life, in which administration of 500 micrograms clomiphene will result in subsequent anovulatory sterility and pyosalpinx. These results demonstrate that the induction of anovulatory sterility and pyosalpinx is dependent upon the dose of clomiphene and the age of rats at clomiphene injection.