AIM: To assess the usefulness of two independent histopathological classifications of rectal cancer regression following neo-adjuvant therapy.METHODS: Forty patients at the initial stage cT3NxMO submitted to preoperative radiotherapy (42 Gy during 18 d) and then to radical surgical treatment. The relationship between "T-downstaging" versus regressive changes expressed by tumor regression grade (TRG 1-5)and Nasierowska-Guttmejer classification (NG 1-3) was studied as well as the relationship between TRG and NG versus local tumor stage ypT and lymph nodes status,ypN.RESULTS: Complete regression (ypTO, TRG 1) was found in one patient. "T-downstaging" was observed in 11 (27.5%) patients. There was a weak statistical significance of the relationship between "T-downstaging"and TRG staging and NG stage. Patients with ypT1 were diagnosed as TRG 2-3 while those with ypT3 as TRG5.No lymph node metastases were found in patients with TRG 1-2. None of the patients without lymph node metastases were diagnosed as TRG 5. Patients in the ypT1 stage were NG 1-2. No lymph node metastases were found in NG 1. There was a significant correlation between TRG and NG.CONCLUSION: Histopathological classifications may be useful in the monitoring of the effects of hyperfractionated preoperative radiotherapy in patients with rectal cancer at the stage of cT3NxMO. There is no unequivocal relationship between "T-downstaging"and TRG and NG. There is some concordance in the assessment of lymph node status with ypT, TRG and NG.TRG and NG are of limited value for the risk assessment of the lymph node involvement.