The purpose of this study is to examine whether the transdermal testosterone system (TTS) is effective and safe in the treatment of hypoactive sexual desire disorder (HSDD) in postmenopausal women who are on transdermal estrogen.

This is a randomised, double-blind, placebo-controlled, parallel-group, multicentre, 24 week study to be conducted in approximately 300 patients at approximately 14 clinical sites in the UK, 6 sites in Australia, 5 sites in Germany, and 2 sites in Canada. Women will be randomised 1:1 to receive 300 mcg/day TTS or placebo for a 24 week period. Consistent with previous phase III studies, efficacy will be assessed over 24 weeks using the Sexual Activity Log (SAL), and at 12 and 24 weeks using the Profile of Female Sexual Function (PFSF) and Personal Distress Scale (PDS). Safety will be assessed over the entire 24 weeks. Hormone data (free and total testosterone, total estradiol, and sex hormone binding globulin) will be collected at Weeks -4 and 24. The total duration of treatment for each patient is 24 weeks.

Inclusion Criteria:

• Women will be screened for study participation according to the following inclusion criteria at Week -4. Eligible women must be a woman one year post menopausal, 40-70 years old in general good health on transdermal HRT and in a stable monogamous sexual relationship with low sexual desire causing distress.

Exclusion Criteria:

• Women will be screened for study participation according to the following exclusion criteria at Week -4 or as specified. Eligible women must not have any medical, physical, psychological, or pharmacological condition that could confound safety or efficacy.