BACKGROUND: The Parenting Stress Index-Short Form (PSI-SF) is one of the most widely used instruments for measuring parenting stress in families of children with autism spectrum disorders (ASD). However, no research to date has examined the psychometric properties of the PSI-SF in a sample of parents of young children with ASD. In this regard, item response theory (IRT) can be used to estimate how much information or discrimination each item of a scale offers across the entire range of the latent variable being measured, by creating individual item information curves or profiles. The purpose of this study was to use IRT to examine the discriminability of PSI-SF items in a sample of parents of young children with ASD who experience varying levels of parental stress. METHODS: The study involved the parents of 141 children with autism spectrum disorders (91.4% mothers; mean age 36.2 years) who completed the PSI-SF following diagnosis. Item characteristic curves were constructed for each of the PSI-SF items and examined with regard to item functioning. RESULTS: Results indicated that, for the most part, changes in parental distress severity were reflected in changes on item scores. However, several items on the subscales measuring parent-child dysfunctional interactions and child behavior difficulty functioned poorly to discriminate parents across a range of total stress severity. CONCLUSIONS: The parent-child dysfunctional interaction and difficult child subscales of the PSI-SF scale should be used with caution with parents of young children with ASD. More research is required to examine PSI-SF content validity, at least among parents of children with ASD and perhaps parents of children with other disabilities as well.