One hundred and three patients aged 80 years or more were operated on for colorectal cancer (n = 80) or gastric cancer (n = 23). The postoperative mortality rate was 8%. Hospital mortality (12%) was not influenced by the factors age or emergency procedure, but by the factors ASA score (P = 0.06), palliative procedure (p = 0.08), and gastric surgery (P = 0.05). The overall 5-year survival rate was 23% after colorectal surgery, and 10% after gastric surgery (P = 0.001). After colorectal surgery, long-term survivals were observed, even in presence of serosal and/or lymph nodes involvement. Thirteen patients were alive more than five years after surgery. In contrast, after gastric surgery, all patients, except those with early carcinoma, died within one year. Indications for operation must be wide in colorectal cancers, and more restrictive in gastric cancers. Long-term survivals were observed after colorectal surgery in the elderly, even in the presence of lymph node involvement. In contrast, after gastric surgery, all patients, except those with early carcinoma, died within one year.