BACKGROUND: Studies evaluating the efficacy of routine follow-up testing in detecting disease recurrence in treated lung carcinoma patients are lacking. METHODS: To investigate this subject, the authors studied 115 patients who had previously been entered on North Central Cancer Treatment Group (NCCTG) small cell lung carcinoma clinical trials, had achieved a complete response after chemotherapy/radiotherapy treatment, and subsequently developed disease progression. The authors included 58 patients with limited stage and 57 patients with extensive stage disease. Follow-up testing on these clinical trials was scheduled at 4-month intervals in the first year and every 6 months thereafter. At each visit, testing included a clinical history, physical examination, chest X-ray, chemistry group, and hematology group. Patients' records were evaluated to determine the first test(s) to identify disease recurrence, whether the recurrence was diagnosed at the time of routine follow-up or between scheduled follow-up evaluations, the sites of recurrence, and patient outcome. RESULTS: Recurrences occurred in 56 patients (49%) in the first follow-up year, 51 (44%) in the second year, and 8 (7%) after 2 years. Recurrences were signaled by clinical histories in 71% of patients, by physical examinations in 10%, chest X-rays in 12%, and abnormal chemistry testing in 6%. Although 41% of recurrences were detected at scheduled clinical visits, 59% of patients had disease recurrence signaled by symptoms that prompted interval visits between scheduled appointments. At last follow-up, all the patients in this study had died (median survival, 115 days [range, 1-793 days] after diagnosis of recurrence), supporting the lack of curative therapy for patients with recurrent small cell lung carcinoma. CONCLUSIONS: These data, demonstrating that clinical histories and physical examinations are the most fruitful means of detecting evidence of recurrent lung carcinoma, are consistent with data regarding the follow-up of other curatively treated cancers, such as breast carcinoma and melanoma. Chest X-rays in asymptomatic patients detect recurrences in a small proportion of patients, whereas routine blood tests appear to be of little value.