Brain activity in people with high-functioning autism has been shown to be atypical in a number of ways, including reduced synchronization across areas of activation measured by functional magnetic resonance imaging. This activation atypicality has been observed mostly during the performance of cognitive tasks. This study compares the resting-state network of 57 participants with autism and 57 control participants matched for age and intelligence quotient. The results indicate that both groups have a resting-state network that is very similar both in volume and in organization, but in autism this network is much more loosely connected. This functional underconnectivity was observed in the anterior-posterior connections. The results expand the theory of cortical underconnectivity in autism to the resting state of the brain. © 2006 Lippincott Williams & Wilkins, Inc.