Agrobacteria are noted primarily for their phytopathogenicity and when isolated from human clinical specimens are often considered contaminants or organisms of low pathogenicity. We report six cases at one hospital over a 6 1/2-year period in which infection was accompanied by a compatible clinical syndrome and review 19 cases reported in the literature. Fourteen of the 25 combined cases involved central venous catheter-associated infections. Six cases involved peritonitis, five of which occurred in patients undergoing continuous ambulatory peritoneal dialysis. Additional infections included two non-catheter-associated bacteremias, one prosthetic valve endocarditis, and two urinary tract infections. Most infections were community acquired, and restriction enzyme analysis of Agrobacterium isolates from eight patients at one hospital revealed unique patterns in each case without evidence for clonal dissemination of these strains. Agrobacterium isolates may be resistant to multiple antibiotics, and optimal therapy has not yet been determined. Agrobacteria should be recognized as opportunistic pathogens in the immunocompromised host, particularly in those with indwelling plastic catheters.