The dietary importance of beta-carotene as a factor in health maintenance has recently attracted considerable interest. Previously, total carotene content was estimated in a limited number of human tissues by means of spectrophotometric methods. In this study the levels of beta-carotene were measured by high-pressure liquid chromatography in tissue samples of uterine leiomyomas and adjacent normal myometrium obtained at hysterectomy from uteri of 18 patients. beta-Carotene concentration was significantly (p = 0.0013) lower in fibroid tissue than in normal myometrium. In addition, levels of beta-carotene were assayed in tissue samples of cancers of the cervix, endometrium, ovary, breast, colon, lung, liver, and rectum and were compared with levels of respective adjacent normal sites. The concentrations of beta-carotene were found to be lower in all cancer tissues. The decreased levels of beta-carotene suggest that beta-carotene deficiency may have a role in the cause and/or pathogenesis of leiomyomas and cancers of the organs that were investigated. The mechanism of action, however, remains unknown.