OBJECTIVE: To study the relationship between intracellular actin and scar contracture. METHODS: Fibroblasts from 10 cases of hypertrophic scar and 5 cases of keloid were cultured in vitro. Total actin, filamentous actin(F actin), globular actin (G actin) and the ratio of F to G actin(F/G) were measured by densitometry after differential extraction and separation by polyacrylamide gel electrophoresis in the presence of sodium sulfate. RESULTS: Total actin, F actin, G actin and F/G in hypertrophic scar fibroblasts were 2.38 ng/10(4) cells, 0.98 ng/10(4) cells, 1.42 ng/10(4) cells and 0.68 respectively, while in keloid fibroblasts were 1.68 ng/10(4) cells. 0.46 ng/10(4) cells, 1.26 ng/10(4) cells, and 0.36 respectively. There was significant differences between two tissues fibroblasts in the items of total actin, F actin, G actin, and F/G (P lt; 0.01), while no significant difference in G actin (P gt; 0.05). CONCLUSION: Total intracellular actin, F actin, and F/G may play an important role in the scar contracture. The hypertrophic scar and keloid can be distinguished by the contents of total intracellular actin, F actin and F/G.