Bacillary angiomatosis (BA) is an unusual systemic vascular proliferation seen predominantly in patients with the acquired immunodeficiency syndrome. These vascular lesions are probably due to infection with a Bartonella species, most often B. henselae and, in some patients, B. quintana. BA is treatable and often curable, but without therapy, may be life-threatening. Clinically, the lesions, when superficial, are said to often resemble pyogenic granulomas, appearing polypoid histologically with an epidermal collarette. We now report six patients, three of whom showed lesions of BA morphologically and histologically distinct from the other patients reported to date. Two patients lesions appeared clinically as violaceous plaques and tumours resembling Kaposi's sarcoma; one of them had lesions histologically reminiscent of a papular angiokeratoma; and the other had lesions histologically suggestive of a combination of Kaposi's sarcoma and BA. Another patient presented with soft subcutaneous nodules which histologically showed extensive acute inflammation characteristic of an acute abscess, but which also displayed proliferating dilated small blood vessels with bulbous endothelial cells adjacent to numerous bacteria and also containing them. The Grocott-methenamine silver stain and the Warthin-Starry stain showed the organisms to better advantage in lesions of all six patients, although bacteria were also evident with the haematoxylin and eosin, periodic acid-Schiff and alcian blue stains.