In addition to the major human immunoglobulin heavy-chain locus on chromosome 14q32.3, VH and D segments are known to be present on chromosomes 15 and 16, We have now amplified and sequenced 24 such VH segments from somatic cell hybrids and have assigned them to 15q11.2 and 16p11.2 using cosmid and yeast artificial chromosome clones. In addition, we have located a cluster of D segments on 15q11.2, previously thought to be located on 14q32.3. We propose that the segments on chromosome 16 arose by an interchromosomal duplication and identify the corresponding region on chromosome 14. Taken together with the completion of a map of the human VH locus on 14q32.3, the total number of VH segments now identified is 117. We can now account for most, if not all human germ-line VH segments.