Leukocyte alkaline phosphatase (LAP) scores in peripheral blood, and plasma carcinoembryonic antigen (CEA) levels were determined in 122 colorectal cancer patients, and compared to 30 healthy persons, who served as controls. Both markers are gradually elevated according to the severity of tumor penetration. LAP scores in Dukes’C and D (157 ± 79) were significantly higher than in Dukes’A, Bi and B2 (81 ± 43), p < 0.001. CEA levels were also higher in Dukes’ C and D (50 ± 95) than in patients with Dukes’ A, Bi and B2 (25 ± 54), p < 0.07, but less significantly. The LAP score has at least the same reliability as the CEA values as a marker of stage in colorectal cancer patients.