Female gender is a significant independent favorable prognostic factor in lung cancer. To study the possible role of sex hormones in lung cancer, the expression of sex-steroid receptors and the glucocorticoid receptor was investigated in 29 lung-cancer cell lines stemming from small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC) by means of immunocytochemistry, ligand-binding assays and RNA expression via polymerase chain reaction. In at least 2 methods of investigation, NSCLC cell lines showed a low expression of estrogen receptor in 6, progesterone receptor in 13 and androgen receptor in I2 out of 17 cases examined; sex-steroidreceptor expression was virtually absent in SCLC cell lines. The glucocorticoid receptor was expressed in all 29 cell lines studied. Additionally, 52 tumor samples from primary lung cancer were investigated for their receptor expression by means of immunohistochernistry. Among patients with primary lung-cancer sex-steroid-receptor expression in tumor biopsies was detected most frequently in female patients (in 69% of I6 cases, vs. 42% of 36 tumors from men) and in patients with adenocarcinoma. Further research will focus on these subgroups. lmmunohistology is a feasible method of studying steroid-receptor expression in lung cancer.