Although the terms “sex” and “gender” are commonly used as synonyms, they refer to two distinct concepts. Sex refers to the biological differences between men and women, whereas gender refers to socially defined roles, behaviours and expectations. Being clear about the distinction between the two terms is important, as the contribution to women’s health of sex and gender are likely to be different, and therefore also our solutions for reducing disparities. Sex differences are increasingly recognised as being important for conditions such as cardiovascular disease,1 for example, and while physiological differences in coronary vasculature can contribute to different presentations and manifestations of disease, gender influences health behaviours, risks, and access to health services.2 We argue that taking gender into account, as well as sex, is critical to improving health outcomes.