Despite the absence of side effects reported in the small studies for relatively short periods of time done up till now in women with testosterone treatment, in the treatment of a long term disorder such as diminished sexual desire it is reasonable to be concerned with androgenizing side effects. Therefore, it would be extremely useful if testosterone could be given on a prn (as needed) basis before sexual intercourse. Recently Tuiten et al [2000] studied normal volunteer women with vaginal flow measures using photoplethysmography in addition to questionnaire data on sexual arousal after exposure to erotic movies with pre treatment of sublingual testosterone vs. placebo in a single dose sublingually of 0.5mg. Testosterone significantly enhanced vaginal blood flow response to the erotic movies and also the subjective sexual interest, desire and arousal to the movies. The psychophysiological effect was maximal 4 hours after the sublingual testosterone. Blood levels of 25nmol/L testosterone, 10 times baseline, were maximal 10 minutes after sublingual delivery and returned to baseline within 90 minutes.