The expression of the p53 and Rb1 proteins was examined in an unselected consecutive series of 250 primary operable colorectal carcinomas with a mean follow-up of 4.3 years (range 43-77 months). The overall cancer-specific mortality was 34.8%, with 87 cancer deaths and 35 deaths as the result of other causes. Expression of p53 protein was identified in 152 of 250 (60.8%) cases, with expression of Rb1 protein in 207 of 250 (82.8%) cases. There was no association of p53 or Rb protein expression with patient age, sex, tumour site, tumour size, tumour type, tumour grade, peritumoral fibrosis, tumour lymphocytic infiltrate, nature of the tumour margin, extramural vascular invasion, number of lymph nodes or high apical lymph node involved or local peritoneal infiltration by tumour, Dukes' stage or Jass group. There was no difference in overall survival or recurrence-free survival for those cases that showed p53 expression or Rb1 protein expression compared with those cases showing absence of p53 or Rb1 protein expression, although patients with tumours showing aberrant (reduced) Rb1 protein expression demonstrated shorter recurrence-free survival and overall survival. The effect of 'aberrant' Rb1 protein expression and shorter recurrence-free and overall survival did not, however, achieve independent statistical significance. The results from this study would suggest that expression of p53 and Rb1 proteins does not appear be useful in determining the prognosis of operable colorectal cancer.