The incidence of atypical mycobacteriosis is rising, however, the clinical, pathologic and radiographic aspects of atypical mycobacteriosis are generally indistinguishable from those of tuberculosis. There is much differences in epidemiology, diagnosis and therapy between them, it should be clearly differentiated from tuberculosis. At this point, were reviewed 19 cases of confirmed mycobacteriosis and 100 cases of usual tuberculosis by the way of chest film, and found certain roentgen features that might suggest the possibility of atypical mycobacteriosis as follow. 1. Among the 19 cases of atypical mycobacteriosis, group III (Nonchromogens) is highest in number of 12 cases but groupI(photochromogen) is not noticed. 2. Inspite of the advanced extent of disease in roentgenogram, tuberculin skin tests are negative or weakly positive. 3. Cavitation appears to be more common with atypical mycobacteriosis than tuberculosis. Multiple thin walled cavities are more prominent and the i cidence of air fluid level in the cavity is somewhat higher than tuberculosis. 4. The presence of preexisting pulmonary disease if more noted in atypical mycobacteriosis particularly of emphysema. 5. Lack of fibrosis, calcification and hilum elevation with healing process of atypical mycobacteriosis is charactristic findings. 6. Atypical mycobacteriosis are frequently resistant to antituberculous drug therapy, so roentgenological improvement in 1 year follow up film shows less effectiveness in atypical mycobacteriosis with even aggravation. 7. Extrapulmonary manifestations of atypical mycobacteriosis are noted in 3 cases due to group III, involving lumbar spine, meninges and large bowel.