Gender bias has implications in the treatment of both male and female patients and it is important to take into consideration in most fields of medical research, clinical practice and education. Gender blindness and stereotyped preconceptions about men and women are identified as key causes to gender bias. However, exaggeration of observed sex and gender differences can also lead to bias. This article will examine the phenomenon of gender bias in medicine, present useful concepts and models for the understanding of bias, and outline areas of interest for further research.