Seven cases of Alcaligenes xylosoxidans bacteremia and/or respiratory disease in patients infected with the human immunodeficiency virus (HIV) are described. Reported only thrice previously in this setting, these bacterial complications occurred during different phases of HIV infection and were associated with leukopenia-neutropenia in four patients and a central vascular catheter in two. Although the majority of cases were diagnosed after day 3 of hospitalization, a distinct source of infection was never identified. In four patients with advanced underlying disease, a polymicrobial infection was present. In vitro resistance to aminoglycosides, first-generation cephalosporins, and aztreonam was identified, but treatment with fluoroquinolones, piperacillin, or an aminoglycoside in combination with either ceftazidime or pefloxacin was successful in all cases. The relevance of Alcaligenes xylosoxidans and related species of gram-negative non-glucose fermenting bacilli as opportunistic pathogens in the immunocompromised host and in the setting of HIV infection is briefly reviewed.