The primary purpose of this study was to examine the underlying factor structure of the Parenting Stress Index-Short Form (PSI-SF) in a large cohort of parents of young children with autism spectrum disorder (ASD). A secondary goal was to examine relationships between PSI-SF factors and autism severity, child behavior problems, and parental mental health variables that have been shown to be related to parental stress in previous research. A confirmatory factor analysis (CFA) was used to examine the three-factor structure described in the PSI-SF manual [Abidin, 1995]: parental distress, parent-child dysfunctional interaction, and difficult child. Results of the CFA indicated that the three-factor structure was unacceptable when applied to the study sample. Thus, an exploratory factor analysis was conducted and suggested a six-factor model as the best alternative for the PSI-SF index. Spearman's correlations revealed significant positive correlations with moderate to large effect sizes between the revised PSI-SF factors and autism severity, externalizing and internalizing child behaviors, and an index of parent mental health. The revised factors represent more narrowly defined aspects of the three original subscales of the PSI-SF and might prove to be advantageous in both research and clinical applications. Autism Res 2011,4:336-346. © 2011 International Society for Autism Research, Wiley Periodicals, Inc.