These studies provide evidence for slowed spatial orienting of attention in autism. A group of well-defined adult autistic subjects and age-matched normal controls performed a traditional spatial cueing task in which attention-related response facilitation is indexed by speed of target detection. To address the concern that motor impairment may interfere with interpretation of response time measures in those with neurologic abnormality, we also used a new adaptation of the traditional task that depended on accuracy of response (target discrimination) rather than speed of response. This design allowed separation of time to process and respond to target information from the time to move and engage (orient) attention. Results from both tasks were strikingly similar. Normal subjects oriented attention very quickly, and showed maximal performance facilitation at a cued location within 100 ms. Autistic subjects oriented attention much more slowly and showed increasing benefits of a spatial cue with increasing cue-to-target delays. These results are consistent with previous reports that patients with autism, the majority of whom have developmental abnormalities of the cerebellum, as well as those with acquired damage to the cerebellum, are slow to shift attention between and within modalities. This paper also addresses the variability in behavioral findings in autism, and suggests that many of the apparently contradictory findings may actually reflect sampling differences in patterns of brain pathology.