Despite growing controversy surrounding its use as a "morning after pill," diethylstilbestrol (DES) is prescribed liberally for rape victims. Guidelines for its use in these patients is lacking. Of 150 consecutive rape victims treated at a university medical center, 63 (42 percent) received prescriptions for DES. Of the 55 (87 percent) on whom follow-up was obtained, in 40 (73 percent) there were substantial side effects-nausea or vomiting, or both. At least six (11 percent) did not complete therapy because of these side effects. The authors offer guidelines for use of DES for rape victims and a plan for patient education and follow-up.