The initial study describing the development of the Multidimensional Scale of Perceived Social Support (MSPSS) indicated that it was a psychometrically sound instrument (Zimet, Dahlem, Zimet, & Farley, 1988). The current study attempted to extend the initial findings by demonstrating the internal reliability, factorial validity, and subscale validity of the MSPSS using three different subject groups: (a) 265 pregnant women, (b) 74 adolescents living in Europe with their families, and (c) 55 pediatric residents. The MSPSS was found to have good internal reliability across subject groups. In addition, strong factorial validity was demonstrated, confirming the three-subscale structure of the MSPSS: Family, Friends, and Significant Other. Finally, strong support was also found for the validity of the Family and Significant Other subscales.