Blood groups in 2,935 Roms (Gypsies) of East Slovakia show the following frequencies of phenotypes and genes: A1A2BO phentopes: A1--32.91%, A2--2.42%, B--25.21%, O--30.15%, A1B--8.45%, A2B--0.85%, A1--0.2363, A2--0.0217, B--0.1929, O--0.5491. MN phenotypes: M--27.16%, MN--51.60%, N--21.23%, m--0.5297, n--0.4703. RH phenotypes: Rh positive--89.54%, Rh negative--10.46%; Rh - (D)--0.6766, Rh (d) 0.3234. The frequencies are contrasted with those of other inhabitants, non-Roms of East Slovakia.