Aims: Venous invasion is an established predictor of prognosis in colorectal cancer (CRC). The reported incidence of venous invasion in CRC specimens varies between 10% and 89.5%, mainly as a result of interobserver variability and differences in specimen processing (for example, staining with haematoxylin and eosin (H+E) alone versus the addition of an elastic fibre stain). This study was performed with three purposes in mind, namely: (1) To assess and compare the incidence of venous invasion diagnosed on H+E stained tissue versus tissue stained with both H+E and an elastic fibre stain. (2) To estimate the inherent false negative rate associated with the diagnosis of venous invasion by histopathological evaluation of resected CRC specimens. (3) To compare the resulting data regarding incidence, quantity, site, and type of venous invasion to the pertinent literature. Methods: Venous invasion was assessed on sections from 81 CRCs resected from patients with synchronous distant metastases (hepatic and non-hepatic). Only stage IV tumours were studied for the following reasons: (1) it can be assumed that in all patients with distant haematogenous metastases venous invasion had occurred, thus enabling the false negative rate to be calculated; (2) there can be no dispute about the clinical relevance of the various characteristics of venous invasion identified in the tumours of patients with synchronous distant haematogenous metastases; and (3) to eliminate the effect of variance in tumour stage on the incidence of venous invasion. Initially, H+E stained sections were studied for venous invasion. Sections that were negative or questionable with regard to venous invasion were then stained with an elastic fibre stain, and a second search for venous invasion was carried out. Venous invasion was characterised by incidence, quantity, type, and site. The χ 2 test for independence was used to compare the incidence of venous invasion in colonic versus rectal and rectosigmoid primary tumours, and in patients with hepatic versus non-hepatic metastases. Results: Venous invasion was identified in 42 (51.9%) (of the 81 specimens on H+E stained sections. The addition of the elastic fibre stain enabled the diagnosis of venous invasion in 15 (38.5%) of the remaining 39 specimens, increasing the overall incidence to 57 of 81 cases (70.4%). Of the 57 positive specimens, venous invasion was minimal in 27 (47.4%), intermediate in five, (8.8%) and massive in 25 (43.9%). Only intramural veins were involved in 18 (31.6%), only extramural veins in 26 (45.6%), and both intramural and extramural veins in 13 (22.8%) of the 57 positive specimens. The filling type of venous invasion was found in 41 (71.9%), the floating type in 28 (49.1%), and the infiltrating type in six (10.5%) of the 57 positive specimens. There was no significant difference between the incidence of venous invasion in the colon (42 of 60; 70%) versus rectal and rectosigmoid tumours (15 of 21; 71.4%; p = 0.8539), nor in the incidence of venous invasion in patients with hepatic (...