Two cases of bronchial carcinoid without discernible distant metastasis and without the carcinoid syndrome are reported. In both cases preoperative diagnosis was facilitated by finding hyperserotoninemia and increased urinary 5-HIAA. Following surgery, the values returned to normal, indicating that resection was complete. Both tumors contained increased amounts of serotonin. Pertinent features of previously reported serotonin-producing lung tumors are reviewed. The finding of increased indoles in these 2 cases without the clinical carcinoid syndrome is not surprising, in view of current evidence which suggests that most carcinoid-type bronchial adenomas produce some serotonin. It is concluded that urine and blood indole studies may aid in diagnosing bronchial adenomas, even in the absence of distant metastases and the carcinoid syndrome.