Objectives: The purpose of the study was to compare the efficacy of a product containing cranberry and propolis (DUAB) to placebo for reducing frequency of cystitis in women with recurrent acute cystitis. Method: A multicenter, placebo-controlled, randomized study of women aged >18 years with at least 4 episodes of cystitis in the previous 12 months was performed. The number of cystitis episodes over a 6-month follow-up was the primary end point. Results: Forty-two women were included in the cranberry + propolis group, and 43 women were in the placebo group. The mean age was 53 ± 18 years, with 6.2 ± 3.6 cystitis episodes in the previous year, with no differences between the 2 groups. The mean number of infections was lower in the propolis + cranberry group (respectively, 2.3 ± 1.8 vs. 3.1 ± 1.8). The total number of cystitis episodes in the first 3 months was lower in the propolis + cranberry group (0.7 ± 1.1 vs. 1.3 ± 1.1, p = 0.0257) after adjusting for water consumption. The mean time to onset of the first urinary tract infection (UTI) was also significantly longer in the propolis + cranberry group (69.9 ± 45.8 days vs. 43.3 ± 45.9, p = 0.0258). Tolerance to the treatments was good and comparable in both groups. Conclusions: We demonstrate for the first time that cranberry and propolis supplementation significantly reduces the incidence of UTIs during the first 3 months and delays the onset of an episode of cystitis.