The menstrual history of 162 cases of female lung adenocarcinoma and 19 cases of squamous cell carcinoma was compared with 187 age-matched female controls, and analyzed for statistical significant differences that may exist between the two groups using the Epi-infor program, the Chi-square test, and the Bartlett test for homogeneity of variance. Parameters related to menstrual history included: age of menarche, menstrual cycle, number of days of menstrual period, amount of menstrual flow, menstrual pain, breast bloating/tenderness, and total number of menstrual cycles prior to menopause or diagnosis of lung cancer. The results show that cases of squamous cell carcinoma have a higher total number of menstrual cycles than controls, raising the possibility that estrogen may play a role in the induction of squamous cell carcinoma. Cases with adenocarcinoma were found to have shorter menstrual periods than controls, suggesting that activity of the corpus luteum may be related to the occurrence of adenocarcinoma. Progesterone (PR) and estrogen (ER) receptor levels were also measured in 21 adenocarcinoma surgical specimens. A positive ER and PR receptor expression was correlated with later menarche and earlier menopause.