OBJECTIVES: To investigate whether the preventive use of cranberry capsules in long-term care facility (LTCF) residents is cost-effective depending on urinary tract infection (UTI) risk. DESIGN: Economic evaluation with a randomized controlled trial. SETTING: Long-term care facilities. PARTICIPANTS: LTCF residents (N=928, 703 female, median age 84), stratified according to UTI risk. MEASUREMENTS: UTI incidence (clinically or strictly defined), survival, quality of life, quality-adjusted life years (QALYs), and costs. RESULTS: In the weeks after a clinical UTI, participants showed a significant but moderate deterioration in quality of life, survival, care dependency, and costs. In high-UTI-risk participants, cranberry costs were estimated at Euro 439 per year (1.00 euro=1.37 U.S. dollar), which is Euro 3,800 per prevented clinically defined UTI (95% confidence interval=Euro 1,300-infinity). Using the strict UTI definition, the use of cranberry increased costs without preventing UTIs. Taking cranberry capsules had a 22% probability of being cost-effective compared with placebo (at a willingness to pay of Euro 40,000 per QALY). In low-UTI-risk participants, use of cranberry capsules was only 3% likely to be cost-effective. CONCLUSION: In high-UTI-risk residents, taking cranberry capsules may be effective in preventing UTIs but is not likely to be cost-effective in the investigated dosage, frequency, and setting. In low-UTI-risk LTCF residents, taking cranberry capsules twice daily is neither effective nor cost-effective.