The purpose of this study was to assess the timeliness of initial antibiotic administration and culture acquisition for Medicare patients discharged with a principal diagnosis of urinary tract infection. The main outcome measurement was reduced length of stay. Data were collected retrospectively from 24,389 randomly selected discharged Medicare patients from September 1, 1994, to August 31, 1995. Only 61% of the cases as urinary tract infection had adequate criteria to confirm the diagnosis. Of these cases, antibiotics were administered within 4 hr after presentation in 40.9% patients. Urine cultures within 24 hr of presentation were noted more frequently (94%)than blood cultures (66%). Urine cultures obtained before antibiotic administration were noted more frequently (82%) than were blood cultures (58%). Timely antibiotic administration and the acquisition of urine cultures in the first 24 hr of hospitalization were independently associated with shorter length of stay.