['Perioperative blood transfusion has been associated with increased tumour recurrence and poor prognosis in colorectal cancer. Blood loss in the peritoneal cavity might be a tumour-promoting factor for local recurrence. The aim of this study was to investigate whether blood in the peritoneal cavity affects local tumour recurrence.', 'In an established in vivo rat model the effect of 1.5 ml syngeneic whole blood on tumour cell adhesion and tumour growth was investigated. In the same model the effect of 1.5 ml pure red blood cell (RBC) concentrate and 1.5 ml RBC-derived substances on tumour cell adhesion was studied. In an established in vitro model the effect of increasing numbers of RBCs (0-250 bx 10(6)) on tumour cell adhesion and tumour growth was assessed.', 'Both the presence of blood and RBC concentrate in the peritoneal cavity prevented tumour cell adhesion in vivo (overall P </= 0.001 and P </= 0.05 respectively), rather than promoting adherence. RBC concentrate and RBC-derived substances had a comparable inhibitory effect on tumour cell adhesion. In in vitro studies RBCs inhibited tumour cell adhesion but not tumour growth.'] Do red blood cells inhibit tumour cell adhesion to the peritoneum?