Basic fibroblast growth factor (bFGF) is a potent mitogenic and chemotactic factor for endothelial cells and fibroblasts. To investigate the pathological role of bFGF in hypertrophic scar, we performed an immunohistochemical study on bFGF and bFGF receptor (bFGF-R) in hypertrophic scar (HS) including keloid, in comparison with normal scar (non-HS) and normal skin. To identify bFGF and bFGF-R positive cells, double immunostaining with antibody to mast cell (MC, tryptase) or tissue macrophage (CD68) was carried out. The expression of bFGF and bFGF-R in cultured fibroblasts from scars was also examined. In HS, many positive cells for bFGF or bFGF-R were observed between collagen bundles in addition to the positive area in normal skin. Although most of the positive cells for bFGF or bFGF-R were fibroblasts, the positive rates of bFGF in macrophages was also increased (p < 0.005). The positive rate of bFGF in MCs and the positive rates of bFGF-R in macrophages and MCs were not changed. No obvious difference was observed between non-HS and normal skin in the expression of bFGF and bFGF-R. Cultured fibroblasts from HS showed a strong nuclear staining of bFGF, but not from non-HS and normal skin. bFGF-R was equally expressed with a diffuse cytoplasmic pattern by fibroblasts from all sources. bFGF may play an important role in the pathological fibrotic process of HS in which fibroblasts are persistently activated. Cellular source of the abnormal bFGF in HS may be both fibroblasts themselves and macrophages.