Background: Early intervention is recommended for autism spectrum disorders but often this is delayed because children have not received a formal diagnosis. Nonetheless parents are likely to identify features of ASD from an early age. The main aim of this study was to document through thematic analysis how parents described the features that alerted them to the childs difficulties. Method: From a population of children diagnosed at a specialist, community-based clinic, 72 parents agreed to be interviewed at home about their recollections of early difficulties which were analysed thematically. Results: Two-thirds of parents reported the child's problems were apparent by 18 months with speech and communication difficulties, along with behaviour problems, being the most commonly reported. Statistical analyses identified some relationships between certain features and the age of the child when they became apparent. Clusters of features were also identified. Conclusions: It is argued that health visitors and childcare personnel should be knowledgeable about the early signs of ASD and of the strategies required to promote the development of children whose parents report these early features of ASD. They should be proficient in sharing their knowledge with parents so that assessment and intervention can begin earlier.