<p>Sex and gender may influence the epidemiology, pathogenesis, and prognosis of cancer. This narrative review describes sex and gender differences in the epidemiology and pathogenesis of cancer, and how such differences may impact the pharmacodynamics and pharmacokinetics of cancer treatment. For most types of cancer unrelated to reproductive function, incidence is higher in males than in females, except for gallbladder and thyroid cancers, which are much more common in women. Cancer mortality is higher in men than women; women account for a larger proportion of survivors. These differences may be related to biological differences in pathogenesis or differences in behaviors relating to cancer risk or detection. The pharmacokinetics and pharmacodynamics of cancer therapies also differ between sexes due to differences in body composition, physiology, and receptor expression. Overall, sex and gender are essential variables to be considered in research and clinical practice, influencing diagnosis, subtyping (biomarkers), prognostication, treatment, and dosage.</p>