Early detection of autism plays an important role in enhancing developmental outcomes for affected children. Identifying potential characteristics of the disorder evident during infancy and toddlerhood aids efforts to screen for such symptoms, which may lead to earlier and more accurate diagnoses; however, it is unclear to what extent certain factors encourage or impede early detection. Because parents are responsible for making decisions on behalf of their children based upon their perceptions of children's developmental progression, caregivers were queried in terms of their beliefs about the development of autism characteristics in their children. Participants included 393 caregivers of children with autism, Asperger's syndrome, and PDD-NOS from the U.S. and 5 other English-speaking countries who completed an online questionnaire containing both closed- and open-ended questions. Rich, descriptive information on children was provided in terms of demographic variables, comorbid diagnoses outside of the autism spectrum, the type of autism onset (congenital or regressive) children experienced, the presence of a family history of autism or other mental-health disorders, and the ages at which behavioral difference were detected for 11 early symptoms indicative of autism. Analyses were conducted with the last 4 variables within this list and with an additional variable reflecting parents' beliefs about the etiology of autism (genetic versus some external mechanism). Significant relationships existed between a variety of these variables with the exception of a family history of autism or other mental-health disorders. About half of the sample reported that their children developed autism in a congenital fashion while the remaining half, a regressive fashion. Those indicating a congenital onset reported noticing all 11 early characteristics at younger ages relative to those indicating a regressive onset; however, significant differences between groups existed for only 4 of these 11 early symptoms. Parents who indicated a congenital onset were also more likely to espouse a genetic etiology for autism relative to parents indicating a regressive onset who were more likely to attribute the disorder to some external mechanism. Type of autism onset and presence versus absence of child comorbidity independently predicted the ages at which parents detected anomalies in 7 of the 11 early characteristics. Interpretations of the findings are discussed in detail, followed by suggestions for future directions of research in this area.