Benign prostatic hyperplasia (BPH) is one of the common disease in elderly men. Recently old-age population is increased and we are growing more and more interested in clinical importance of BPH. In this study, the effect of PLX, which was the mixture of tomato extract (including 2% of lycopene) and chitooligosaccharide, on prostatic cancer cell and testosterone-induced BPH in adult rats of the Sprague Dawley strain was determined. The cell viability was evaluated by MTT method using L929 and LNCaP cell line, pretreated with various concentrations of PLX. The expression of prostatic specific antigen (PSA) and 5${alpha$}$-reductase genes were evaluated by realtime PCR using LNCaP cell line and compared various concentrations of PLX with 50 ${mu}$M of finasteride. An experimental prostatic hyperplasia was induced in male Sprague Dawley rats by giving testosterone for 8 weeks. After 2 weeks from start of giving testosterone, PLX and finasteride were administered orally once a day. The results were analyzed with prostate weight per body weight at 8 weeks. Cell viability of L929 cell line decreased specifically at the concentration of 2000 ${mu}$g/mf of PLX. The cytotoxicity of PLX to the LNCaP cell line was shown at above 500 ${mu}$g/ml of PLX. The inhibitory effect of PLX to the expression of PSA and 5${alpha$}$</TEX>-reductase genes in LNCaP cell line increased with the concentration of PLX. In vivo study, the results of PLX and finasteride administered group were 3.75${pm}$0.60 and 3.49${pm}$0.49 prostate weight ${ imes}10^3$/body weight, which were lower than the result of BPH induced group (4.74${pm}$0.58). These results suggested that PLX may be an effective material in BPH by having the role of the 5a-reductase inhibitor.