Osthole, 7-methoxy-8-[3-methylpent-2-enyl]coumarin (1), was extracted from a Chinese herb Cnidium monnieri (L.) Cuss. It showed immunity strengthening, anti-tumor, anti-hepatitis, and anti-osteoporosis activities in previous studies. Our goals are to study the effects of 1 on cell proliferation and TGF-beta of hypertrophic scar fibroblasts. Our results showed that 1 induced apoptosis and inhibited cell proliferation in hypertrophic scar fibroblasts. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that its IC(50) value toward hypertrophic scar fibroblasts was 15.5 +/- 2.2 micromol/l. Furthermore, the results of cell growth curve matched with the above results. Inducing apoptosis by 1 in hypertrophic scar fibroblasts was assessed by various morphological and biochemical characteristics, including cell shrinkage, chromatin condensation, membrane blebbing, formation of apoptotic bodies, and DNA ladder formation. A typical 'Sub-G(1) peak' was also checked through flow cytometry. We used immunohistochemistry to observe the expression of TGF-beta(1). Also, we found that 1 could obviously inhibit the expression of TGF-beta(1) of fibroblasts derived from hypertrophic scar compared with the control group (P < 0.05). These results suggest that 1 inhibits the growth of hypertrophic scar fibroblasts through apoptosis and decreases the expression of TGF-beta(1).