The success of sildenafil in the treatment of erectile dysfunction has led to efforts to find similar treatments for prevalent disorders of female sexual dysfunction. Daily transdermal testosterone has been shown to improve sexual function in women after oophorectomy (Shifren et al, Transdermal testosterone treatment in women with impaired sexual function after oophorectomy, New England Journal of Medicine, 343; 682-8, 2000). In laboratory measures of sexual arousal, a single application of transdermal testosterone enhanced vaginal blood and increased erotic fantasy in normal volunteer women in the laboratory setting, four hours after application (Tuiten et al, Can sublingual testosterone increase subjective and physiological measures of laboratory-induced sexual arousal?, Arch Gen Psychiatry, 59;465,2002). We therefore planned a study of transdermal testosterone (25mg) marketed as Androgel in female hypoactive sexual desire disorder. Patients are recruited from the sexology clinics at Soroka Hospital and the Beersheva Mental Health Center. They are randomized to Androgel or placebo and given 10 packets and instructed on application to the abdomen and shoulders, four hours before planned intercourse. Patients unable to discuss planned intercourse with their partner are offered psychosexual counseling and those still unable after three sessions are excluded. After one month patients on active Androgel are crossed over to placebo or vice versa. Patients self-rate sexual response after each intercourse using the Brief Index of Sexual Functioning for Women, and Arizona Sexual Experiences Scale (ASEX)-Female and are rated in interview at the end of each month of treatment using the Sexual Function Questionnaire (SFQ-V1). Our prn technique avoids the androgenizing side effects of continuous daily treatment.