Serum samples from 226 Gypsies were tested for Gm(1,2,4,5,8,10,11,14,17, 21,23,25) and for Inv(1,2). The Gm phenotypes found are very numerous and the more frequent among this population are: Gm(4,5,8,10,11,14,23,25); Gm(1,4,5,8,10,11,14,23, 25), Gm(1,4,5,8,10,11,14,17,21,23,25), Gm(1,4,5,8,10,11,14,17,23,25) and Gm(1,2,4, 5,8,10,11,14,17,21,23,25). All the phenotypes except three can be explained by nine haplotypes: Gm4,5,8,10,11,14, 23,25, Gm4,5,8,10,11,14,23,25, Gm4,5,8,10,11,14,25, Gm1,17, 21, Gm1,10,11,17,25, Gm1,2,17,21, Gm1,8,17,21, Gm1,8,17,21,23 and Gm1,5,10,11,14,17. Thehaplotypes Gm1,7,21, Gm1,2,17,21, Gm4,5,8,10,11,14,25 (with or without Gm[23]) are all three common among Caucasoids, Gm1,10,11,17,25, Gm1,4,5,10,11,14,23,25 (common among Mongoloids) and Gw1,5,10,11,14,17 (common to Negroids). For the Inv system, this population possesses a very low frequency of Inv(1) and Inv(2).