SummaryWe examined the expression of the transglutaminase 1 (TGase 1) gene IN frozen sections of normal and psoriatic epidermis by means of non‐radioactivein situhybridization with digoxigenin‐labelied cRNA probes. TGase l mRNA was expressed in the granular layer of normal epidermis. regardless of ortho‐or hyperkeratosis. However, in psoriatic epidermis. TGasel mRNA was detected in the suprabasal spinous layer, but not in the subcorneal layer. These results indicate that TGase 1 gene expression is limited to the last stage of keratinization in normal epidermis and this regulation is disturbed in psor