Genetic polymorphism of serum orosomucoid (ORM1) was investigated in 1072 unrelated German Caucasians using isolectric focusing followed by Western blotting and EIA. The estimated allele frequencies were ORM1 *F1 = 0,5690, ORM1 *S = 0,3927, ORM1 *F2 = 0,0368, ORM1 *F2S = 0,0009 and ORM1 *F5 = 0,0005. The method was successfully applied to determine ORM1 phenotypes in aged blood samples and blood stains. The results indicated that the ORM protein is a informative and remarkably robust blood group system.