In a consecutive series of 326 patients with primary lung cancer, sarcoid reactions were observed in the regional lymph node or resected lung in 7 patients (2.2%). The average age of the 7 patients, 4 males and 3 females, was 54 years, range 45-70. All the patients underwent lobectomy. The sites in which sarcoid reactions were found were the regional lymph node (N) in 3 patients, the lung parenchyma (L) in 2, N and L in 1, and the tumor stroma in 1. The histologic types were adenocarcinoma in 4 patients, squamous cell carcinoma in 2, and small cell carcinoma in 1. Two patients died of recurrence and myocardial infarction, and five patients are alive, range 5-64 months. The patients with lung cancer complicating sarcoid reactions were significantly younger than the control group (p<0.01), and not significant in prognosis. We conclude that the complication of sarcoid reactions do not influence the prognosis, but that the sarcoid reactions may be a local reaction or resistance to cancer cells.