The expression of p53 and HER-2/neu p185 was studied immunohistochemically in 120 paraffin-embeded specimens of colon cancer with specific monoclonal antibodies. Sixty-eight of the 120 patients were positive for p53(57%), and 55 were positive for p185(46%), p53 was always expressed in the cell nucleus, and p185, the cell membrane. The expression of p53 and p185 was not correlated to sex and age of the patients, to primary sites, stages and pathological classification of the tumors. The survival period of patients with positive p53 was shorter than those with negative p53, while p185 expression showed no correlation to the survival period. The results suggest that p53 expression may be of some value in predicting prognosis in patients with colon cancer.