Mesenchymal stem cells (MSCs) are capable of differentiating into a variety of lineages, including bone, cartilage, or fat, depending on the inducing stimuli and specific growth and differentiation factors. It is widely acknowledged that basic fibroblast growth factor (bFGF) modulates chondrogenic and osteogenic differentiation of MSCs, but thorough investigations of its effects on adipogenic differentiation are lacking. In this study, we demonstrate on the cellular and molecular level that supplementation of bFGF in different phases of cell culture leads to a strong enhancement of adipogenesis of MSCs, as induced by an adipogenic hormonal cocktail. In cultures receiving bFGF, mRNA expression of peroxisome proliferator-activated receptor gamma2 (PPARgamma2), a key transcription factor in adipogenesis, was upregulated even prior to adipogenic induction. In order to investigate the effects of bFGF on PPARgamma ligand-induced adipogenic differentiation, the thiazolidinedione troglitazone was administered as a single adipogenic inducer. Basic FGF was demonstrated to also strongly increase adipogenesis induced by troglitazone, that is, bFGF clearly increased the responsiveness of MSCs to a PPARgamma ligand.