Urinary tract infections (UTI) are a major source of morbidity in persons with spinal cord injury (SCI), often prolonging hospitalization, interfering with rehabilitation, and leading to secondary urologic complications. Greater understanding of host and bacterial factors that may predispose to invasive UTI and identification of persons at greatest risk for renal deterioration could facilitate development of measures to improve the quality of life for these individuals. A prospective investigation of host phagocyte-bacterial interactions was undertaken as a means to assess whether persons with SCI who develop renal deterioration may be deficient in this important means by which invasive bacteria are eliminated from tissues. Neutrophil phagocytic and serum opsonic activities against uropathogenic Escherichia coli and Enterococcus fecalis were studied in 17 persons with SCI who had diminished renal function and 25 persons with SCI who had normal renal function. Phagocytic and opsonic activities of neurologically intact persons were also comparatively studied as an additional control group. No differences in efficiency of opsonization or phagocytosis were detected when persons with SCI and impaired renal function were compared with persons with SCI who had normal renal function or neurologically intact controls. Whether biochemical characteristics of urine or other undefined local aspects of the urinary tract influence host-bacterial relationships and urologic outcome following SCI are topics worthy of future investigation.