The mean value of the number of circulating HT 29 tumour cells was 1364±418/200 μl mouse blood in wild-type scid mice (n=23) in comparison with 2282±657/200 μl mouse blood in E- and P-selectin-deficient scid mice (n=21) using the CEA sequences, the difference between both groups being highly significant (P<0.0001). This evidence concerns the gene CEACAM5 and neoplasm.