As the prevalence of human immunodeficiency virus (HIV) infection increases, so does the recognition of unusual manifestations of this syndrome. This study describes two patients who presented with a unique, rare, cutaneous manifestion of HIV infection. One patient developed an aggressive atypical cellulitis and ascending lymphangitis of the hand, which failed to improve following multiple courses of several different antibiotics. The other patient presented with multiple, vascular, nodular lesions, clinically resembling Kaposi's sarcoma. Routine biopsies and wound cultures were not helpful for diagnosis. A definitive diagnosis of bacillary angiomatosis (BA) was made using a special silver-staining (Warthin-Starry) histological technique and electron microscopy. Both patients responded completely to oral erythromycin therapy. BA is a newly recognized bacterial infection caused by bacteria of the genus Bartonella. It is seen primarily in patients with acquired immunodeficiency syndrome (AIDS), and less commonly in patients with other immunosuppressed conditions. The term BA describes the lesion's pathogenesis (infective-bacillary) and clinico-histology (angiomatosis). The causal organism cannot be cultured reliably and is resistant to most antibiotics. This study reviews these two patients, the differential diagnosis of BA, specific confirmatory tests used in diagnosis, and the treatment outcome of this condition. It is important for the plastic surgeon to understand BA, because it can resemble other common presentations, but it can also be associated with internal involvement leading to mortality. However, when recognized, it can usually be cured by oral erythromycin therapy (500 mg qid) for several weeks.