Serum α(1)-acid glycoprotein (α(1)-AG) content, lactic dehydrogenase (LDH) activity, cholinesterase (Ch-Ease) activity, plasma fibrinogen (Fbg) content, hemoglobin content, serum albumin content and erythrocyte sedimentation rate were measured in 117 patients with lung cancer. Significant difference was observed in α(1)-AG as well as Fbg between stage Ⅰ and Ⅱ, in Ch-Ease between stage Ⅱ and Ⅲ and in LDH between stage Ⅲ and Ⅳ. In inoperable cases who did not obtain any clinical improvement during chemotherapy, significant positive correlation was observed between their life spans and α(1)-AG as well as Fbg measured prior to chemtherapy, and as for Ch-Ease negative correlation was observed. More close correlation was obtained between life spans and biological status which was set up following their laboratory data as stated above. Therefore, it seems that biological status are reliable index for estimating life spans of inoperable cases.