A blood typing system comprises a first section having a plurality of lines of test tube holding means. A second section has a plurality of lines of test tube holding means, each line in said second section associated with only one line in said first section. Receiving means positively aligns each line in said second section with its associated line in said first section. Preferably said second section is a removable centrifuge carrier. Other additional means are disclosed which comprise a better blood typing system.