Fourteen patients with advanced epithelial ovarian cancer were treated with oral verapamil 240 to 480 mg daily for 3 days and intravenous mitoxantrone 12 to 14 mg/m2 on the second days of verapamil administration. Courses were repeated at 21 day intervals to a maximum of 4 courses. Most patients had cancers refractory to prior cisplatin or carboplatin, or had cancers which recurred quickly after such treatments. This poor prognostic profile of patients probably accounted for the lack of objective responses to verapamil plus mitoxantrone. Despite maximally tolerated daily oral verapamil doses (480 mg daily) our inability to achieve in vivo levels of verapamil that in vitro have an optimum cytotoxic potentiating effect mitigate against further clinical exploration of verapamil as a sole enhancing agent.