Treatment of mesenchymal stem cells (MSCs) with fibroblast growth factor 2 (FGF-2) during monolayer expansion leads to increased expression of cartilage-related molecules during subsequent pellet chondrogenesis. This may be due to faster differentiation and/or a durable change in phenotype. In order to evaluate changes over time, we assessed chondrogenesis of human MSCs at early and late time points during pellet culture using real-time PCR, measurement of glycosaminoglycan accumulation, and histology. Marked enhancement of chondrogenesis was seen early compared to controls. However, the differences from controls in gene expression dramatically diminished over time. Depending on conditions, increases in glycosaminoglycan accumulation were maintained. These results suggest that FGF-2 can enhance the kinetics of MSC chondrogenesis, leading to early differentiation, possibly by a priming mechanism. Published by Elsevier Inc.