The proportion of women infected with HIV worldwide has grown in recent years. From a transmission pattern that was once predominantly homosexual men and through intravenous use of drugs, the current pattern has become, to a large extent, heterosexual. Women are more vulnerable to be infected with HIV due to anatomical and psychosocial differences. In spite of this changing gender trend in the HIV pandemic, biological, psychosocial, therapeutic, and quality of life aspects have not been examined in detail in women. Moreover, this lack of investigation has relevance in terms of vertical transmission of the infection to newborns. Herein, we review gender differences in HIV, identifying from a gender perspective the biological and social factors with a greater influence on vulnerability to infection, and, on the other hand, examining gender differences with respect to the use of services, treatment, survival, and quality of life. (AIDS Rev. 2010;12:113-20) Corresponding author: Isabel Ruiz-Pérez, isabel.ruiz.easp@juntadeandalucia.es