While a diagnosis of autism spectrum disorder (ASD) is based on impairments and anomalies in the domains of communication, reciprocal social interaction, and restricted and repetitive behaviors, attentional abnormalities have been considered an associated feature of the disorder since it was originally described. Prior research, reviewed in Chapter 1, has demonstrated that individuals with ASD exhibit early and pervasive impairments in the adaptive allocation of attention. The ubiquitous nature of attentional dysfunction in ASD has prompted the hypothesis that aberrant attentional modulation may act as a significant contributing factor in the development of higher-level sociocommunicative deficits. The xviii objective of the studies presented in this dissertation was to further elucidate patterns of attentional strengths and weaknesses in ASD and to examine whether atypical attentional processes are related to core ASD deficits in social and communication functions. The study presented in Chapter 2 employs behavioral and eye-tracking measures to investigate novelty processing in ASD, and, furthermore, examines how sensitivity to new information is related to sociocommunicative impairments in ASD. Chapter 3 presents an investigation of three attentional networks (alerting, orienting, and executive control) and how efficiency of each attentional network is associated with ASD symptomatology. Chapters 4 and 5 present functional magnetic resonance imaging (fMRI) studies of activation and connectivity of attentional networks associated with visual search in ASD, and how behavioral and neural indices of search are related to deficits in social and communicative abilities. Together, results from these studies provide further evidence of atypical attention function in ASD. Moreover, findings from these chapters demonstrate that decreased sensitivity to new information (Chapter 2), reduced alerting efficiency (Chapter 3), and increased search efficiency (Chapter 5) are related to increased symptom severity in children and adolescents with ASD. A preliminary framework for understanding the distinct pattern of attentional strengths and weaknesses, and how these may be related to the development of the triad of impairments and anomalies used to define ASD is outlined. Lastly, potential avenues for future research and possible treatment implications based on the results and conclusions are discussed.