Background: Acute urinary retention (AUR) is characterized by the sudden inability to urinate, which is usually extremely painful and requires catheterization. Prostaglandins play an important role in the genitourinary function as they provoke contractions of the detrusor muscle. Relaxation of the detrusor muscle, via the inhibition of the prostaglandin synthesis, could result in AUR. Methods: We conducted a population-based case-ontrol study within the Integrated Primary Care Information project in the Netherlands to investigate whether the use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with an increased risk of AUR. All men 45 years or older registered in the database between 1995 and 2002 and with at least 6 months of valid history were included. Cases were all men with a validated diagnosis of AUR. To each case, up to 10 controls were matched on age and calendar time. Results: Within the source population of 72 114 men, we identified 536 cases of AUR and 5348 matched controls. Risk of AUR was 2.02-fold higher in current users of NSAIDs than in nonusers (95% confidence interval, 1.23-3.31). The highest risk for AUR (adjusted odds ratio, 3.3; 95% confidence interval, 1.2-9.2) was observed in patients who recently started using NSAIDs and in those using a dose equal to or higher than the recommended daily dose. Conclusion: This study shows that the risk of AUR is about 2-fold higher in men who use NSAIDs.