Summary Question Are antibiotics for three days as effective as antibiotics for seven days in older women with urinary tract infection? Study design Double-blind randomised controlled trial. Main results There was no significant difference in bacterial eradication rates between groups at two days after completion of treatment (3 day 98% vs. 7 day 93%, p = 0.16 ). Similarly, there was no significant difference in re-infection rates six weeks after treatment. Three-day antibiotics significantly reduced the mean number of adverse events compared with 7-day antibiotics (0.9 vs. 1.6 at 5 days and 1.2 vs. 2.1 at 9 days, both p = 0.001 ). Authors’ conclusions A shorter course of antibiotics was as effective as a longer course in older women with urinary tract infection, and was better tolerated.