Vorozole is a triazole derivative which binds to the cytochrome P450 moiety of aromatase, thus causing reversible inhibition of the enzyme. Plasma estradiol levels are reduced by about 90% in postmenopausal women treated with vorozole. Phase II clinical studies found vorozole to be an effective agent for the treatment of postmenopausal women with advanced breast cancer, achieving objective responses in up to 35% of patients. In 2 large phase III studies, vorozole 2.5 mg/day demonstrated favourable clinical efficacy compared with aminoglutethimide and megestrol. Vorozole improved patients' quality of life to a greater extent than aminoglutethimide. Clinical trials to date indicate that the tolerability of vorozole is better than that of aminoglutethimide. Vorozole also appears to be at least as well tolerated as megestrol (although inappropriate bodyweight gain is more common in megestrol recipients). The most common adverse events with vorozole are hot flushes, and nausea, which are generally mild in severity.