Although there has been increasing interest in asexuality during the past decade, still little is known on this topic. To define asexuality, three different approaches have been proposed: a definition that is based on sexual behavior, one on sexual desire/sexual attraction, one on self-identification, and one on a combination of these. Depending on the definition used, reported prevalence rates range from 0.6% to 5.5%. In this article, the authors present characteristics of asexuality and review biological, psychological, and sociodemographic factors associated with asexuality. Given the suggestion of existing overlap with hypoactive sexual desire disorder, special attention is paid to similarities and differences between this condition and asexuality. It is further noted that theoretical models to understand (the etiology) of asexuality are underdeveloped.