Although the early behaviors associated with autism spectrum disorder have been well characterized, many behaviors are also commonly observed in young children with other developmental delays and even in those with typical development. Therefore, consideration must be given to whether a child demonstrates sufficient autism spectrum disorder symptoms to warrant this diagnosis. Using the Toddler Autism Symptom Inventory, we examined caregiver endorsement of specific behaviors in three groups of toddlers referred for autism spectrum disorder risk: those who received a best-estimate diagnosis of autism spectrum disorder, those with another developmental disorder, and those who showed slight or no developmental delays and did not meet criteria for any disorder. The results revealed significant differences in symptoms among the three diagnostic groups, as well as low frequency of some DSM-5, ASD criteria, especially insistence on sameness, for those with ASD. These findings have important implications for applying the DSM-5, diagnostic criteria to toddlers.