Bacillary angiomatosis (also called epithelioid angiomatosis) is a newly recognized disease most often characterized by a cutaneous infection with reddish papules of vascular origin. It is caused by a weakly reactive gram-negative bacillus, which can be easily demonstrated in tissue sections with the Warthin-Starry stain. Bacillary angiomatosis usually responds readily to treatment with oral erythromycin, 250 to 500 mg, taken four times a day for 2 weeks to 1 month. Because the skin is the most common site of involvement, it is important that the dermatologist recognize this unusual condition. It is essential that treatment be started as soon as possible because deaths may result from visceral and mucosal involvement. The clinical, histologic, and microbiologic aspects of bacillary angiomatosis are discussed and depicted in detail and speculations regarding the pathogenesis are rendered.