Among 22,816 inguinal hernia repairs done between 1950 and 1988, 15 patients (0.07%) had metastatic tumors found within their hernias. Inguinal herniation was the initial sign of cancer in six patients. A palpable inguinal mass (53%) and abdominal or groin pain (67%) were the most common presenting sign and symptom, respectively. Primary tumor sites included the gastrointestinal tract (40%), ovary (20%), prostate (13%), mesothelium (13%), and unknown sites (13%). The median patient survival was 20 months and depended on the primary tumor site. Grossly apparent inguinal hernia sac abnormalities should be examined microscopically to avoid missing the diagnosis of metastatic cancer, but routine histologic examination of all hernia sacs is not warranted.