The aim of this study was to examine the psychological well-being of mothers and the psychological development of their 3-year-old triplet children conceived by in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI). Comparisons were carried out between a sample of 10 families with IVF/ICSI triplets and matched groups of 15 families with IVF/ICSI twins and 30 families with IVF/ICSI singletons. The families were recruited from Follow-Up, a national organization in France that was established to study children conceived by assisted reproduction. Standardized measures of the mother's emotional well-being and of the children's psychological development were administered. Mothers with a multiple birth were found to experience greater difficulties in parenting than mothers of singletons, with no differences between mothers of triplets and mothers of twins. Regarding the children, there were no differences in emotional or behavioural problems between triplets, twins and singletons. However, the triplets and twins showed a delay in some aspects of language development in comparison with the singleton children.