Skin biopsy specimens from 3 consecutive patients with lesions of Kaposi's sarcoma limited to the skin were cultured for bacteria, and also examined histopathologically for the presence of acid-fast wall deficient (CWD) bacteria. Corynebacterium sp and Propionibacterium acnes were isolated from two repeated cultures from the first case. Both Staphylococcus epidermidis and Streptococcus viridans were isolated from the second case. Bacteriologic culture of the third case was negative. Utilizing the Intensified Kinyoun stain for the detection of acid-fast CWD bacteria, variably acid-fast coccoid forms were visualized in the tissue sections from two cases. In one case, the Gram strain revealed similar forms. Newer knowledge linking CWD bacterial forms of staphylococci, streptococci, and corynebacteria-like microbes to cryptic infection of human blood is discussed, as well as the possible role of CWD bacteria in the pathogenesis of malignancy. This study suggests that CWD microbes might play a role in the pathogenesis of Kaposi's sarcoma, and that the presence of microbes might be detected by bacteriologic culture of KS lesions, and acid-fast histologic staining of skin biopsy specimens.