Studies on the segregation of the red blood cell determinant Xg in 12 families with X-linked inheritance of agammaglobulinemia (XLA) in 3-4 generations suggested linkage of Xg with XLA. One extensive pedigree of a Dutch family with XLA in eight generations was investigated for Xg and the quantitative polymorphism 12E7. LIPED analysis indicated linkage disproven up to 25cM distance within this pedigree. Taken together with data obtained from two other informative XLA pedigrees and with published data, the results indicate no close linkage between XLA and Xg: 12E7, the distance between XLA and Xg being more than 20cM.