Seven kinds of serum regulatory gene coding protein for cell growth were determined with enzyme linked immunodotting in 19 indoor coal-burning exposed patients with lung cancer (Group A), 22 exposed cases without lung cancer (Group B), and 19 nonexposed cases without lung cancer (Group C) to study pathogenesis of lung cancer patients exposed to indoor coal-burning. Results showed that serum concentrations of ras, p53 and neu protein in Group A were significantly higher than those in Groups B and C, with a statistically significant difference (P < 0.05) or a very significant difference (P < 0.01). Six cases in Group A were positive for ras protein (with two strong positive), three for p53, neu and jun each, and one for p16. Two in Group B were positive for ras protein and one for p16. It suggests that serum regulatory protein for cell growth can be regarded as biological markers for environment-related lung cancer.