In previous studies of orosomucoid (ORM) types and disease the ORM1 1 type has been found to be associated with sarcoidosis and other immunogenetic diseases, and the ORM 1 2 type with different types of carcinomas. We report significant associations between ORM1 and C3 types in sarcoidosis and breast cancer, but not in healthy individuals. The ORM1 1 and C3S variants in combination increased the risk of sarcoidosis, and the ORM1 2 and C3F variants together gave an increased risk of breast cancer. A probable mechanism may be that the ORM1 and C3 molecules modify the immune response by interacting with the lymphoid cell surface.