The human growth hormone (hGH) in lung cancer was studied immunohistochemically in 160 patients by the PAP method. Thirty-four neoplasm specimens (21.3%) contained hGH-positive tumor cells. Positive reaction for hGH was shown in 19 of 64 squamous cell carcinomas, 13 of 48 adenocarcinomas, 2 of 5 carcinods, and none of 26 small cell carcinomas and 17 large cell carcinomas. The sensitivity for hilar type lung cancer was higher than that for peripheral type (p<0.05). Positive rates for hGH were not affected by age, sex, tumor size, lymph node involvement or postsurgical stage. The survival rate of hGH positive patients was not worse than that of hGH negative.