The aim of this study was to further expand these data by Smad4 mutation analysis of a large set of early-stage (I–III) colorectal cancer patients treated in a randomised multicentre trial of 5-fluorouracil (5-FU)/Mitomycin C adjuvant chemotherapy of the Swiss Group for Clinical Cancer Research (SAKK study 40/81). This evidence concerns the gene SMAD4 and colorectal cancer.