The authors studied 118 patients with colon cancer (65 males and 53 female) admitted and operated at the Surgical Department of the Casalpusterlengo Hospital (Milan, Italy); over a period of 5 years (1986-1990). All patients were submitted to a pre-op. work-up with Barium enema, colonoscopy, abdominal ultrasound exam, and PAP-test and mammogram for females patients. We found 7 cases (5.9%) of multiple synchronous colon cancer (in 4 patients 2 cancers and in 3 patients 3 cancers). We also found extracolonic malignancy in the same patients (1 synchronous and 2 metachronous). New criteria are proposed to distinguish multiple colon cancers from multifocal colon cancers. It may be concluded that every patient with colo-rectal cancer requires a complete pre-op. examination of the colon and some tests to rule out other extracolonic malignancy.