A cross-sectional analysis was used to examine age-related differences in ASD symptoms and corresponding differences in disruptive behavior and social skills in 281 adult men with fragile X syndrome. Four age groups were created: 18-21, 22-29, 30-39, and 40-49 years. The 18-21 year-old group was reported to have more impairments in verbal communication than the 22-29 year-old group and more restricted and repetitive behaviors than the 40-49 year-old group. There was not an age-group difference in the percentage of men who met criteria for an ASD diagnosis based on respondent-reported, current symptoms. There was a trend for an age-related difference in disruptive behavior. Findings add to understanding of the developmental trajectory of ASD symptoms in adulthood.