Twelve cases of multiple primary bronchogenic carcinoma out of 745 operated and pathologically confirmed ones are reported, with an incidence of 1.6%. There were 1 female and 11 males. The ages ranged 36-72 with a mean value of 61.9. Eleven had double and 1, had triple lesions. The pathologic relationship was squamous-squamous carcinoma in 4 cases, squamous-small cell carcinoma in 3, squamous-adenocarcinoma in 1, undifferentiated-giant cell carcinoma in 1, bronchiolo-alveolar bronchiolo-alveolar carcinoma in 1 and adeno-adenocarcinoma in 1. The triple primary lesions were all adenocarcinoma. The cause of increase in incidence, clinical manifestations, diagnosis, differential diagnosis and surgical treatment are discussed.