Classical Tibetan medicine is closely related to Buddhist philosophy. This article describes how the study and meaning of sexual differentiation in Tibetan medicine is deeply rooted in Buddhist texts and philosophy. The article pays particular attention to the Buddhist theory of mutual dependence of birth and death and on the medical ways of explaining the determining of sex. While Tibetan medicine approaches sexual differentiation by examining its various determinant factors, thus aiming to improve understanding of the human body and diseases, which manifest differently in men and women, in Buddhist philosophy sexual differentiation is perceived as a fundamental, natural phenomenon of human life that forms a key in Tantric practices to comprehend the nature of mind and thence attaining the highest state of mind. The article consists of a translation of the first chapter of a Tibetan medical book on obstetrics, including a newly written introduction to the Buddhist interpretive frame employed in the chapter.