Orosomucoid (ORM) is a polymorphic acute-phase reactant with immunosuppressive properties. Previous investigations have suggested that ORM and other acute-phase reactants may act as blocking factors protecting tumor cells against immunological attack, thereby contributing to the 'immune escape' of the tumor. ORM types were studied by isoelectric focusing and immunoprinting in patients with carcinoma of the breast, lung, ovary and endometrium and in population controls. In accordance with a previous study, the frequencies of the ORM1*2 allele and the ORM1 2 phenotype were found to be significantly increased in patients with different types of carcinomas. The results suggest that the ORM1 2 variant may influence the progression of cancer by being more immunosuppressive than the ORM1 1 variant. The relative risk for carcinoma in patients with the ORM1 2 type was 1.56 (95% confidence interval:1.16-2.09).