The tumour suppressor gene p53 is altered in most colorectal tumours. We found that lymphatic dissemination was driven by the presence of mutated p53 whether or not the cell contained wild-type p53. In a total sample of 187 specimens, point mutation of the p53 gene occurred in 70% and 43% of cases with and without lymph-node involvement, respectively. By contrast, haematogenous dissemination was apparently the result of absent functional wild-type p53 (whether or not the cell contained mutated p53). These results are of potential importance in the prediction of the clinical behaviour of a tumour.