The majority of women with anovulation or oligo-ovulation due to polycystic ovary syndrome (PCOS) have clinical and/or biochemical evidence of hyperandrogenism. This chapter describes treatment with clomifene, aromatase inhibitors, gonadotrophins, and metformin. Weight loss has the undoubted advantages of being effective and cheap with no adverse effects and should be the first line of treatment in obese women with anovulatory infertility associated with PCOS. The aromatase inhibitors letrozole (Femara, Novartis) and anastrozole (Arimidex, AstraZeneca) have mainly been employed for the treatment of postmenopausal women with advanced breast cancer. In women with PCOS, metformin is said to lower fasting insulin concentrations but also probably acts directly on theca cells and attenuates androgen production. There is now sufficient evidence that low-dose step-up gonadotrophin therapy should be preferred to the now outdated conventional therapy for anovulatory patients and particularly for those with PCOS.