The prevalence of autism spectrum disorders (ASD) continues to be a source of debate among researchers and clinicians. Prevalence studies are of the utmost importance in order to obtain an accurate picture of the true prevalence rate of ASD and because these rates continue to be on the rise. To date, studies examining prevalence rates have utilized community or clinical populations. Therefore, the aim of the current study was to utilize a sample of toddlers at risk for or currently diagnosed with a developmental delay (N = 2027) to determine the prevalence rate in this young population. As anticipated, the prevalence rates of ASD were much higher in this at risk sample of toddlers compared to rates reported in community or clinical samples. In addition, gender differences in prevalence rates emerged. However, the differences between these rates were not as pronounced as in other previously studied populations. These results underscore the necessity to routinely assess toddlers for the presence of symptoms of ASD who are already receiving early intervention services for other developmental delays. (Contains 2 tables.)