Chest radiographic (mainly CT), and pathological findings in pulmonary infarction associated with lung cancer were studied to obtain information useful for the interpretation of CT findings, and to help determine the cause of infarction. Sixteen cases of lung infarction were chosen from among 518 cases of lung cancer. All patients were operated on between January 1980 and December 1990. Sixteen surgical cases and one autopsy case all with evidence of lung cancer and infarction were chosen. There were 13 men and 4 women with a mean age of 56 years. Adenocarcinoma was found in 8 cases, squamous cell carcinoma in 6, adenosquamous carcinoma in 2, and small cell carcinoma in 1. Chest radiographs and CT revealed infarction shadows in 8 of the 16 cases. Typical CT findings for pulmonary infarction were:shadows located in the same lobe and periphery as the cancer; ill-defined, 10-25 mm nodular shadows; and lesions located both in the subpleural zone and apart from the pleura. Lesion counts in each area were about the same. Observation of one patient for 2 months revealed a decrease in the size of the nodular shadows and clarification of their margins. In most cases, centrally extended cancer resulted in vascular stenosis and infarction.