Rates and onset of regression were meta-analyzed from 85 articles representing 29,035 participants with autism spectrum disorders (ASD). Overall prevalence rate for regression was 32.1, 95% CI [29.5, 34.8] occurring at mean of 1.78 years, 95% CI [1.67, 1.89]. Regression prevalence rates differed according to four types of regression: language regression, 24.9%; language/social regression, 38.1%; mixed regression, 32.5%; and unspecified regression, 39.1%. Regression prevalence also differed according to sampling method: population-based prevalence was 21.8%, clinic-based prevalence was 33.6%, and parent survey-based prevalence was 40.8%. Risk of regression was equal for males and females, but higher for individuals diagnosed with autism versus another ASD. Later age of regression onset was predicted by older age of child.