Between 1972 and 1990, 456 patients with locally advanced colorectal carcinomas (tumor stage T4) were operated. In 187 cases the operation was extended by multivisceral resection and in 269 patients a conventional resection was performed. The rate of curative R0-resections was 74.9% for the extended resection group compared to 66.2% for the conventional group. The postoperative mortality after extended resection was 4.9% (2.9% conventional resection). Analyses of long-term results showed a 5-year survival for all R0-resected cases of 52.1% +/- 4.1. Further evaluation of additional lymph-node involvement in T4 colorectal tumors revealed significant differences in 5-year survival: 64.8% T4N0; 27.9% T4N1,2; 9.2% T4N3 for conventional R0-resection and 59.9% T4N0; 23.2% T4N1,2; 6.6% T4N3 for extended R0-resection. After curative resection (R0) the presence or absence of intraoperative tumor-cell dissemination could be identified as a significant prognostic factor. In all cases of T4 colorectal carcinomas-especially for N1-3-an adjuvant treatment after conventional or extended R0-resection is recommended.