During a pathologic examination, cancer nodules, and not lymph node metastases, are often seen in the fatty tissue outside the rectum. The significance of this type of cancer spread, which is called extrabowel skipped cancer infiltration (ex), was investigated. A total of 369 patients who underwent resection of rectal adenocarcinoma between 1980 and 1992 were reviewed. All surgical specimens were examined microscopically to determine if ex existed in the fatty tissue outside the rectum or in the detached fatty tissue around the dissected lymph nodes. The ex was divided into four patterns: scattering (sct), vessel invasion (ves), neural invasion (ni), and nodular (nd). Ex was found in 130 patients (35.2%). Of these, 19 were sct, 58 ves, 21 ni, and 111 nd. The overall recurrence rates after curative resection were 52.8% in the ex(+) group and 24.0% in the ex(-) group (P < 0.001). The local recurrence rates were 35.8% and 14.9%, respectively (P < 0.01). The ex(+) group exhibited a significantly worse survival than the ex(-) group (P < 0.001). The presence of ex indicates the aggressive biologic activity of rectal cancer. Ex may be a significant prognostic predictor in these patients. Therefore, such treatments as extended dissection, postoperative adjuvant therapy, and a meticulous follow-up are all considered to be necessary for patients with ex.