Expression of VH-coded mRNA molecules in T cells, antigen-specific T cell lines, or T cell hybridomas was not detected using four different VH DNA probes under conditions that permitted cross-hybridization between distantly related VH genes. In contrast, VH gene expression was readily detected in two B cell lymphomas and in splenic B cells. Less than one molecule per cell of RNA, exactly complementary to the DNA probes used, would have been detected in these T cell populations. The results thus seriously question the proposition that T cells use the B cell VH repertoire to code for antigen receptors.