Earlier identification and diagnosis of autism spectrum disorders (ASDs) can improve opportunities for children to benefi t from early intervention and lessen the burden on concerned parents. This review summarizes current knowledge about early signs of autism and early it diagnosis. Many data from different retrospective and prospective studies of high-risk infants indicate that ASD symptoms emerge in the first two years of life, affecting multiple developmental domains, mapping onto symptom dimensions consistent with current diagnostic frameworks including social-communication, and repetitive interests/behaviors but also extending to motor delays and atypical regulation of attention and emotion. Recent findings have shed new light on patterns of symptom onset and progression, and promise to inform early detection and diagnosis. Further attention to effective application of new fi ndings and related challenges in building health system capacity to ensure timely access to specialized assessment and interventions is needed to fully realize the promise of improved outcomes resulting inclusivly from this research.