The maps of the human immunoglobulin heavy-chain and kappa light-chain loci have recently been completed. We have now completed a map of the human lambda locus (IGL) located on chromosome 22q 11.2. We mapped 52 Vλ genes from 10 Vλ families and 7 Jλ and Cλ genes on a 1140 kb contig constructed from eight YACs and 129 cosmid clones. The Vλ genes are arranged within 800 kb. Genes of the different Vλ families are organized in three clusters, Vλ ll and lll families (cluster A); Vλ l, V, VII and IX families (cluster B); Vλ IV, VI, VIII and X families (cluster C), in contrast to the dispersed organization of the different VHand VK families within the human VHand VK loci. We note that the most frequently used Vλ families (Vλ ll and lll) are proximal to the Jλ and Cλ genes. The Vpre B gene, encoding part of the surrogate light chain, the GGT2 gene and the BCRL4 were also mapped within the lambda locus.