Research findings examining the adjustment of siblings of children with autism has been inconsistent, with some studies concluding that siblings are negatively impacted, while others have found no adverse effects. We argue that one reason for these inconsistent findings may be the failure by some investigators to take into account the increased genetic vulnerability faced by siblings of children with autism. In this study, we assessed the adjustment of siblings, with and without a diagnosed non-medical disability or disorder, using the "Strengths and Difficulties Questionnaire" [Goodman, R. (2001). "Psychometric properties of the Strengths and Difficulties Questionnaire". "Journal of American Academy of Child and Adolescent Psychiatry", 40, 1337-1341]. When compared to non-diagnosed siblings and a large normative sample, diagnosed siblings scored significantly higher in terms of adjustment difficulties and lower in terms of prosocial behavior. In addition, in hierarchical regressions, several child, parent, and family factors were found to be significant predictors of adjustment among non-diagnosed siblings when assessed 2 years latter, while no explanatory variables were significantly linked to latter adjustment outcomes among siblings with a diagnosed disability or disorder. Study limitations and implications are discussed. (Contains 6 tables.)