A preponderance of males with autism spectrum disorders (ASD) has been evident since the initial writings on the topic. This male predominance has consistently emerged in all ASD research to date in epidemiological as well as clinical populations. Despite this long recognized gender disparity in ASD, surprisingly there is a paucity of research addressing gender as it relates to core ASD symptom presentation. Gender differences may manifest with regard to symptom domains, severity, breadth, and so forth. The present review will discuss background (e.g., history, prevalence), assessment issues, gender differences in typically developing individuals in domains relevant to ASD, an in depth review of the literature base on the nature and etiology of gender differences in ASD, as well as future research directions and implications.