Little information is available pertaining to infectious morbidity in women with genital malignancy. To define the magnitude of this problem, all patients admitted to the gynecologic oncology services at the University of Michigan Medical Center between January 1, 1986, and December 31, 1986, were followed prospectively for the development of infectious morbidity. One hundred nine bacteriologically confirmed infections occurred in 297 patients during 510 admissions. An additional 31 postoperative patients received empiric therapy for presumed infection. Urinary tract (54) and wound (22) infections were the most commonly confirmed infections. The pathogens isolated from oncology patients were significantly different in frequency of isolation and antibiotic sensitivity when compared with pathogens isolated from women developing infections on the benign gynecology service. Women with genital malignancies are at high risk for the development of a variety of infections by resistant pathogens, emphasizing the importance of obtaining cultures prior to initiation of therapy and carefully selecting the antibiotics to be prescribed.