Over the course of 11 years (1993-2003) we encountered 5 cases of pulmonary nontuberculous mycobacterium (NTM) involving a solitary pulmonary nodule. In this report we analyze the chest computed tomography (CT) of these patients, the utility of bronchoscope and transthoracic fine-needle aspiration techniques, the mycobacterium species involved, and treatment results. Four of the 5 NTM cases were due to infection with M. avium and one was due to infection with M. intracellulare. The characteristic findings of the chest CTs were as follows: A solitary nodule was present just under the pleura. No definite distribution pattern was evident. Some cases had agglutinated nodules or fine calcifications. Although fiberoptic bronchoscopy was not used as a diagnostic tool in all 5 NTM cases and histological samples did not contain granulomas, we determined the presence of NTM and we also verified that no cancer cells were present in any of the 5 NTM patients, using transthoracic fine-needle aspiration. Four out of the 5 NTM patients were treated only with drug therapy and they displayed clinical improvement. We resected a solitary nodule in one of the 5 NTM patients because of slow response to drug therapy. We conclude that the solitary pulmonary nodule of NTM is often due to M. avium and that transthoracic fine-needle aspiration is an easy and effective method of detecting NTM.