We have performed a preliminary study of the efficacy for new medication Infemin based on diindolylmethane (DIM) with improved bioavailability. Eleven patients were included with diagnosed prostatic intraepithelial neoplasia (PIN) and a background of benign prostatic hyperplasia (BPH). First group (4 patients) received Infemin 900 mg pro day, the second group (n=7) received placebo. Efficacy of therapy was controlled using morphological index (MI) in prostate bioptates, revealing the proportion of patients with persisting PIN/BPH at month 12 after treatment start. The prostate volume, urodynamic criteria (Qmax, Qave, Vres), IPSS and quality of life indices and IIEF-based estimation of erectile function were also considered in time points 3, 6, 9 and 12 months after the treatment initiation. MI after 12 months was lower in the Infemin group (dropped from 0,50 down to 0,04), in the control group it was increased from 0,42 up to 0,58 (p=0,008). Full regress of PIN was observed in 50% of cases in study group with no regress cases in the control group (p=0,209). In the Infemin group we have also observed the trend to the reduction of the prostate volume and Vres at 3 months after the treatment beginning (p=0,0497). Quality of life, micturition-related symptoms and erectile function did not show any significant changes from the baseline level.