"Stress proliferation" (the tendency for stressors to create additional stressors) has been suggested as an important contributor to depression among caregivers. The present study utilized longitudinal data from 90 parents of children with ASD to replicate and extend a prior cross-sectional study on stress proliferation by Benson (J Autism Develop Disord 36:685-695, 2006). Consistent with Benson's earlier findings, regression analyses indicated that stress proliferation mediated the effect of child symptom severity on parent depression. Parent anger was also found to mediate the effect of symptom severity on stress proliferation as well as the effect of stress proliferation on parent depression. Finally, informal social support was found to be related to decreased parent depressed mood over time. Implications of study findings are discussed.