T-cell receptor 1 (γ/δ) expression was studied in 19 jejunal or duodenal specimens from patients with dermatitis herpetiformis and in 16 jejunal or duodenal specimens showing normal histology. In normal specimens, γ/δ + cells represented 10.8% of intraepithelial CD3+ lymphocytes. Around 50% of these cells were recognized by the A13 monoclonal antibody, which detects products of the Vγ1/Vδ1 gene rearrangement and the non-disulfide-linked form of T-cell receptor 1. The remaining 50% reacted with the BB3 monoclonal antibody, which recognizes products of the Vγ9/Vδ2 rearrangement and the disulfide-linked form of receptor. Very few γ/δ + cells were observed in the lamina propria. In jejunal specimens from patients with dermatitis herpetiformis, a significant increase in the prevance of γ/δ + intraepithelial lymphocytes was observed (P < 0.001). This finding was largely accounted for by an increase in those cells recognized by the A13 monoclonal antibody, thus possibly expressing the Vγ1/Vδ1 rearrangement and the nondisulfide-linked form of receptor. These data suggest that similar pathogenetic mechanisms may be active in determining the jejunal damage in celiac disease and dermatitis herpetiformis.