Reported is a case of 71-year-old man who had triple primary neoplasms that were diagnosed simultaneously on admission. He visited our hospital for examination of an abnormal mass shadow seen in the right lower lobe of his chest in a roentgenogram. That was determined as being a small cell lung cancer. We simultaneously detected that a moderately differentiated tubular gastric adenocarcinoma and an olfactory groove meningioma were overlapped as well. Attention must be paid to multiple primary neoplasms, since some of these malignancies are predicted to overlap and the percentage of overlapped neoplasms is increasing. Care must be taken to avoid mistaking an overlapped tumor for a metastatic one. In 1986, according to the Annuals of Pathological Autopsy Cases in Japan, 2196 cases that represented 9.4% of all malignancies had overlapped tumors and triple or more overlapped cases amounted to 225 a year. Malignancies in the digestive system, the respiratory system, the urinary tract and in the endocrine system seem to be greatly affected with multiple neoplasms.