In patients with the acquired immunodeficiency syndrome (AIDS), four cases of mycobacterial infection in which bacilli appeared as cylindrical, nonstaining "negative images" have been previously described. These may have been extracellular or within histiocyte cytoplasm, and they have been described in aspirations from liver, lymph node, and bone marrow and in bronchoalveolar lavage fluid. We report three additional examples of this finding in fine-needle aspirations from lymph nodes in AIDS patients infected with Mycobacterium avium-intracellulare. Our findings support the concept that these negative images of bacilli are diagnostic of mycobacterial infection. Air-dried Romanovsky-stained material is required for their identification.