The authors report their experience about the clinical significance of the invasion of veins (BVI) in 68 patients with colorectal carcinoma, submitted to potentially curative surgery in the period 1980-1988. Every patient was screened for BVI. The tumoral spreading was differentiated into endovascular and perivascular permeation. The authors also considered the incidence and kind of BVI, the recurrence rate of the tumour and five-year survival rate. BVI was present in 33 patients (48.5%). Recurrence was observed in 22 patients (22.3%): 19 patients in the group with BVI (33 patients): 3 in the group of 35 patients without BVI. BVI was related to tumour stage, but it may be considered as an independent factor in its relationship with a poorer prognosis in patients affected by tumours in stages II or III; in fact, the patients in stage II had a poorer prognosis than those in stage III without BVI. These results suggest that BVI, as a prognostic factor, is independent from tumoral stage in determining the recurrence rate and the long term prognosis.