Background: Mothers of young children with Pervasive Developmental Disorders (PDD) and other disabilities (DD) have been reported to experience high levels of stress. This investigation examined the effects of parental stress on mother's participation in a Relationship Focused intervention (RFI). Methods: Mothers and young children who had either PDD (n = 18) or DD (n = 26) received weekly RF intervention for one year. Results: Pre-post comparisons indicated significant increases in mother's responsiveness and children's development and social emotional functioning. Intervention effects were greater for mothers of children with PDD than for mothers of children with DD. There were three findings related to the role parenting stress. First, high levels of parenting stress did not interfere with mother's ability to learn RFI strategies; second, there were non-significant decreases in parenting stress during intervention; third, parenting stress enhanced the effects of mothers? responsiveness on children. Conclusion: High levels of parenting stress does not appear to interfere with parent participation in RFI.