The records of 182 consecutive rectal carcinomas treated in this department between JAN 1978 and DEC 1990 were reviewed to assess the outcome of the patients presenting with lateral pelvic lymph node infiltration. Lateral lymph node dissection was carried out in 24 (42.1%) of the 57 Ra tumors and 63 (72.4%) of the 87 Rb tumors, but in none of the 38 cases of Rs tumors. Lymph node involvement was detected 0% and 15.9% of the Ra and Rb tumors, respectively. In this series, none of the cases in which the tumors were confined to m, sm and pm had positive lymph nodes. However, 23.3% of the 43 cases in which invasion was beyond pm showed positive lymph node invasion. The main lymph nodes involved were located in the roots of the middle rectal arteries. Half of the patients presented with distant metastases within one year, with poorer prognosis considering the mean survival rate of 1.8 years. In conclusion, we advocate that in Rb rectal tumors with circular invasion or invasion beyond the pm, careful lateral lymph nede dissection should be carried out. On the other hand, we suggest the use of preoperative radiation therapy which could improve the curability, the disease-free interval, and survival rates.