The results showed the following: the increase of procathepsin B concentration in ascites of patients with ovarian cancer was the highest compared to the serum of controls (elevation about 13-fold, p<0.001) (Fig. 1); with cystatin C being the second highest (p<0.05, elevation about 1.8-fold) (Fig. 3) and cystatin B being the third highest (p<0.001, increase up to 1.4-fold) (Fig. 2). The gene discussed is CSTB; the disease is ovarian cancer.