Abstract: In patients with brochogenic carcinoma of various types and in different stages, serum β₂-m1 croglobulin （β₂-m） and carcinoembryonic antigen （GEG） were determined simultaneously. In cases with advanced lung cancer, the positive rate of β₂-m was 68.3%, and that of GEA, 33.3%; in the stage of CR, they were 29.0% and 3.2% respectively. It was found that there was no correlation between the levels of β₂-m and CEA （r=-0.0621） but between the levels of β₂-m or CEA and clinical manifestations. There was a clear-cut relationship （P＜0.01）. The positive rate of combined determinations of β₂-m and CEA was 43.5%—9.2%, higher than that single determination of CEA. It was also found that in the patients with recurrence the findings of β₂-m were 3—5 months earlier than those of CEA. The false positive rate of β₂-m, however, was rather high. Therefore, combined determinations seems to be useful for monitoring the therapeutic effects and judging the prognosis.