Sexually immature females of Procambarus clarkii were implanted with androgenic glands. Surviving females containing living androgenic gland implants developed first abdominal appendages that were masculine. Many forms of masculinization of these appendages occurred. The first masculine changes were thickening and calcification of the base of each of the pair of first abdominal appendages. On most of the masculinized females, their first pair of abdominal appendages were very similar to that of a male. As a control, immature females were implanted with vasa deferentia only. None of the controls exhibited masculinization of their first pair of abdominal appendages. In masculinized females which became mature, vitellogenesis was inhibited. Development of many oocytes in the ovaries was inhibited.