Autistic children represent a source of stress for their parents, but the most appropriate way to measure this stress is not clear. Two studies in the literature compared parents' and professionals' ratings of symptom severity, and had parents rate the stressfulness of each symptom. The present study sought to replicate past research, and to extend it by validating this method of measuring parental stress compared to more traditional measures. Results indicated that mothers, fathers, and professionals agreed on the severity of child behaviours. Mothers found these behaviours significantly more stressful than fathers. The stress related to specific child behaviours was significantly correlated with more general measures of parental stress.