The comparative incidence of symptomatic vaginal candidiasis associated with pivmecillinam and norfloxacin treatment in women with acute symptomatic uncomplicated UTI was determined in two randomised, double-blind, clinical trials. Adverse events reported following general enquiry were reviewed. Presence of Candida vaginitis was based upon the specification as such by investigators, the presence of specific symptoms such as genital pruritus and/or the prescription of specific anti Candida therapy. The incidences of Candida vaginitis were as follows; Study 1 pivmecillinam 200 mg tid for 7 days 13 (4.6%), pivmecillinam 200 mg bid for 7 days 7 (2.4%), pivmecillinam 400 mg bid for 3 days 6 (2.1%) and placebo 6 (2.1%), P=0.19. Study 2 pivmecillinam 400 mg bid for 3 days 7 (1.5%), norfloxacin 400 mg bid for 3 days 20 (4.3%), P=0.016. The incidence of Candida vaginitis in women with acute symptomatic uncomplicated UTI given 3 days treatment with pivmecillinam 400 mg bid is similar to that seen with placebo and is significantly less than the incidence with norfloxacin 400 mg bid for 3 days.