AIM To investigate the actions of basic fibroblast growth factor (bFGF) on the proliferation and differentiation of the non-adherent stromal precursor (NASP) cells. METHODS The osteogenic potential of the bone marrow stromal cells (BMSC) isolated from Wistar rats were cultured in the absence or presence of bFGF. After ALP cytochemistry, the colonies were counted by image analysis. The cells cultured in petri dishes were stained by the avidin-biotin-peroxidase complex (ABC) immunoperoxidase technique for collagen type Ⅰ, proliferating cell nuclear antigen ( PCNA ) and double staining for calcium and osteocalcin. RESULTS Many stromal precursor cells are present in bone marrow in a non-adherent form. bFGF not only stimulated the proliferation of NASP cells, but also enhanced the differentiation of NASP cells into osteoblasts. CONCLUSIONS NASP cells are possibly the main targets of the anabolic action of bFGF which may play an important role in fracture healing and bone formation.