Background: postcoital cystitis ranks first among recurrent infections of the lower urinary tract in young women. Their prevention is an important medical social issue. Prescription of antimicrobials for these infections increases antibacterial resistance of urinary tract pathogens, thereby requiring the search for alternative preventive strategies for postcoital cystitis. Aim: to assess the effectiveness of diet correction using biologically active food supplement (BAFS) Ecocystin® containing D-mannose and inulin to prevent coitus-related infections of the lower urinary tract (postcoital cystitis) in women. Patients and Methods: 40 sexually active women aged 18–45 (the mean age 31.9±8.8 years) with recurrent coitus-related infections of the lower urinary tract were enrolled. Women were divided into two groups, i.e., the study group (n=22) and the control group (n=18). Study group women received postcoital preventive treatment for the lower urinary tract infections (one sachet of BAFS Ecocystin® containing 1.5 g of mannose and 1.5 g of inulin no later than 2 hours after sexual intercourse and then another 12 hours later). Control group women received no preventive treatment. The primary indicator of the efficacy of postcoital prophylaxis was the rate of recurrent infections of the lower urinary tract. The additional indicator was the severity of clinical presentations assessed by the Acute Cystitis Symptom Score (ACSS) questionnaire. Follow-up was six months. Results: the rate of recurrent infections of the lower urinary tract was significantly lower in the study group compared to the control group. Recurrences were reported in 27.3% in the study group and 77.8% in the control group over months 1–3 (χ2=10.01, p=0.002) and 13.6% and 72.2%, respectively, over months 4–6 (χ2=14.16, p<0.001). The chances for cystitis exacerbation during the first and the second trimester of the follow-up were 2.9- and 5.3-times lower in the study group compared to the control group. During the first trimester of the follow-up, the recurrence rate was 0.45±0.86 per one woman of the study group and 1.55±1.10 per one of the control group (t=3.6, p<0.001). During the second trimester of the follow-up, the recurrence rate was 0.18±0.50 and 1.50±1.20 (t=4.7, p<0.001), respectively. Women who received BAFS Ecocystin® but developed postcoital cystitis reported much lower symptom severity than the control group. As a result, the study group’s quality of life was significantly higher than the control group’s. Conclusions: BAFS Ecocystin® is a highly effective and well-tolerated preventive tool for postcoital cystitis in women and a pathogenetically reasonable alternative for antibiotics. KEYWORDS: postcoital cystitis, infections of the lower urinary tract, recurrent cystitis, Ecocystin, D-mannose, inulin, non-antibiotic prophylaxis. FOR CITATION: Kuz’min I.V., Slesarevskaya M.N., Al’-Shukri S.Kh. Non-antibiotic prevention of postcoital cystitis in women. Russian Journal of Woman and Child Health. 2021;4(3):209–217 (in Russ.). DOI: 10.32364/2618-8430-2021-4-3-209-217.