Autism is characterized by impairments in three areas: (i) reciprocal social interaction; (ii) communication; and (iii) repetitive and stereotyped patterns of interest and behaviour. Despite the finding that parents notice abnormalities and problems with their child's development at a very early age, research shows that diagnoses are often made at an age beyond that recommended for the commencement of early intervention. This paper reviews the range of studies that have sought to elucidate the early features of autism in young, preschool children. Impairments in the capacity for reciprocal social interaction involving preverbal, verbal and non-verbal communication, and play and symbolic behaviour are the key features indicative of autism in infants and preschool children.