Hypersensitivity reaction (HSR) is still a major concern during cancer chemotherapy with paclitaxel. In the present study, we investigated retrospectively the incidence of HSRs to paclitaxel and the risk factors in 105 patients (553 courses) who received adjuvant chemotherapy (paclitaxel and carboplatin) for ovarian cancer. Moderate to severe HSRs that led to cessation or discontinuation of the chemotherapy, including respiratory distress and hypotension, were observed in 14 patients (13.3%) and 16 courses (2.9%), regardless of the use of conventional premedication with glucocorticoid, and histamine H(1) and H(2) antagonists. The incidence of HSRs to paclitaxel in patients with ovarian cancer seemed to be considerably higher than those reported by other investigators in patients with other carcinomas such as non-small-cell lung cancer and breast cancer. Four risk factors were identified: (1) history of mild dermal reactions such as facial flushing and urticaria in previous courses, (2) presence of respiratory dysfunction, (3) obesity (body mass index >25), and (4) postmenopausal at the time of ovariectomy. The incidence of hypersensitivity increased linearly as the number of risk factors increased (r=0.992, P=0.008). It is likely that disappearance of the estrous cycle facilitates the occurrence of HSRs to paclitaxel.