We reviewed 1808 hospital charts representing virtually all patients given a diagnosis of non-small-cell lung cancer in New Hampshire and Vermont between 1973 and 1976 and found that the treatment of patients varied according to their marital status, medical insurance coverage, and proximity to a cancer-treatment center. Patients were more likely to be treated with surgery if they were married (odds ratio, 1.67; 95 percent confidence interval, 1.08 to 2.57) or had private medical insurance (1.52; 1.03 to 2.26). Among patients who did not have surgery, those with private insurance were more likely to receive another form of anticancer therapy--either radiation or chemotherapy (1.57; 1.18 to 2.09). Residing farther from a cancer-treatment center was associated with a greater chance of having surgery. Patients 75 years of age and older were less likely to have surgery (0.16; 0.08 to 0.35) or any other tumor-directed therapy (0.32; 0.19 to 0.54). The relation between the type of treatment and a patient's characteristics was not based on apparent differences in tumor stage or functional status, although both these factors were also strongly predictive of the type of treatment. Despite the fact that privately insured and married patients were more aggressively treated, they did not survive longer after diagnosis. We conclude that for non-small-cell lung cancer, socio-economic as well as medical factors determine treatment.