Sixty-six parents who had conceived by in vitro fertilization (IVF) were compared with 46 matched naturally conceiving control parents regarding psychosocial adjustment and parenting stress 5 years after the birth of their first child. IVF mothers reported a more external locus of control than did control mothers but did not differ on other measures. Within the IVF group, higher levels of treatment predicted lower parenting stress and more defensive responding on the Parenting Stress Index (R. Abidin, 1990). The more positive reporting of high-treatment IVF parents may be attributable to either defensive responding or the fact that they are particularly highly motivated and competent parents. The study findings confirm a growing body of research regarding overall positive adjustment in IVF parents but also highlight the importance of considering individual differences among IVF mothers with respect to treatment experience.