The manifestations of bacillary angiomatosis include diverse cutaneous lesions, visceral parenchymal bacillary peliosis of the spleen and liver, and involvement of single or multiple organ systems. The organisms causing BA are R. henselae and R. quintana, and these organisms have now been cultured from the spleen and cutaneous lesions of BA as well as the blood of patients with visceral and cutaneous BA. The antibiotic regimen of choice for HIV-infected patients is erythromycin 500 mg 4 x a day for 2-4 months, but relapse may necessitate lifelong suppressive therapy. We are maintaining a registry of patients with bacillary angiomatosis and request that we be contacted (415-206-8680, UCSF) if you diagnose a case, preferably before therapy is instituted.