We have studied the organization of the human immunoglobulin heavy‐chain genes by pulse field gel electrophoresis as well as by isolation of cosmid clones. The total length of the heavy‐chain variable region locus was estimated to be approximately 3000 kb. We found that D segments including a recently isolated D5 segment were dispersed among VH segments. We identified a pseudo V segment 18 kb 3′ to the D5 segment in isolated cosmid clones. A 300 kb fragment produced by MluI digestion contained VH, D, JH segments and the distance between VH and D was estimated to be approximately 240 kb. Overlapping cosmid clones containing the human D1, D2, D3, D4, JH, Cmu and C delta genes were isolated. Restriction maps of these regions indicated that the distance between D and JH is about 22 kb. A partial restriction map of the VH locus was constructed using the pulse field gel electrophoresis technique and deletion of VH segments in B cells.