It has been hypothesized that a rearrangement between the delta recombining element (delta Rec) and a pseudo J alpha gene serves to delete the TCR-delta locus before rearrangement of the TCR-alpha genes. We have now sequenced a direct, site-specific rearrangement between the delta Rec element and a pseudo J alpha gene in a human leukemic stem- cell line. Putative "N-sequence" addition was noted at the site of recombination, suggesting that this event occurred at a time when the enzyme(s) involved in N-region addition were active in this cell. This provides support for the view that deletion of the TCR-delta locus is required before rearrangement of the TCR-alpha chain genes.