Since the genes for two of the T cell receptor (TCR) chains (alpha and delta) and for the immunoglobulin (Ig) heavy chains (alpha, gamma, delta, epsilon and mu) are all on the long arm of human chromosome 14, it is of interest to determine if they are genetically linked and, if so, how strongly. We tested genetic polymorphisms of the TCR alpha-locus and Ig gamma-locus in 19 families comprising 107 members, and asssessed the frequency of recombination between the two loci. The results rule out strong linkage: all recombination fractions below 0.26 gave lod scores less than -2 (odds less than 1:100). Combining the data on maternal and paternal meioses, the most likely recombination fraction was 0.5 (nonlinkage).