A matched comparison was made of 157 parents of preschool twins conceived by one of the following: in vitro fertilization (IVF), infertility workup combined with infertility drug treatment, or spontaneously. The Interview Schedule for Social Interaction was used to examine systematically a comprehensive range of social relationships and the asymmetries therein. Overall, IVF parents reported having deficient social relationships compared with non-IVF parents, and this deficiency was both in size and in affective quality of their available relationships. As anticipated, mothers reported less adequate and available social relationships when compared with their spouses. In the event of a significant finding, mothers from the three groups always had lower mean scores than the fathers. The finding of the extent to which IVF parents were not as socially integrated, compared with the other families of preschool twins, highlights the need to strengthen through mutual aid IVF parents' social networks. The data also suggest the need for ongoing patient care by IVF teams and for support groups to be established exclusively for IVF parents of twins.