Immunoglobulin heavy chain gene transcription was studied using DNA transfection. The enhancer element identified in the mouse heavy chain locus was active in pre-B and plasmacytoma cell lines, but no activity was detected in two T cell lymphomas. However, even in the absence of the enhancer, cell type specificity of immunoglobulin gene transcription was still retained. We have used gene fusions to show that transcription cell type specificity is conferred by a VH gene promoter. Deletion analysis of this VH promoter indicates that a conserved octamer found 5′ of the TATA box in immunoglobulin V genes is a functional part of the tissue-specific promoter upstream element.