A retrospective review of patients <40 years (n=91) seen at the Dana-Farber Cancer Institute and Brigham and Women's Hospital from January 1, 1983-January 1, 1993 was carried out. Of 91 patients, there were 43 men and 48 women with a median age of 36 years (range 28-39). Eighty percent of patients were cigarette smokers for a median of 25 pack years (range 2-68). Ninety-one percent were symptomatic at presentation. The ECOG performance status (PS) was 0 or 1 in 83%. At the time of diagnosis 15% had stage I/II, 17% stage IIIA, 22% stage IIIB and 45% stage IV disease. The most common histopathology was adenocarcinoma (46%), followed by small cell carcinoma (14%), squamous cell carcinoma (12%), large cell undifferentiated (8%) and other types (20%). The median survival for all 91 patients was 1 year with 2 and 5 year survivals of 30% and 18% respectively. Five year survival was related to stage of disease: 60% for patients with stage I, 58% for stage II, 36% for stage IIIA, 10% for stage IIIB, and 3% for stage IV disease. Factors that had no significant effect on overall survival included gender, histologic subtype, degree of differentiation, presence or absence of symptoms, and sites of metastases. Factors that adversely affected survival by univariate analysis included advanced stage of disease, poor PS, duration of symptoms for more than 3 months, and 5% or greater body weight loss. By multivariate analysis only stage (P<0.001) and weight loss (P=0.02) affected survival. This data plus results of other published studies show that young patients under age 40 with lung cancer, compared to the more common older patients, have an increased percentage of women, have a longer duration of symptoms, more often have adenocarcinoma with lower frequency of squamous cell carcinoma and sometimes small cell carcinoma, and more often present with advanced disease. Despite these differences, overall patient survival remains poor and is similar to that of older patients.