Because dermatitis herpetiformis is characterized by neutrophilic inflammation and destructive changes in the basement membrane zone, we studied the ill situ expression of interstitial collagenase and stromelysin-1. in 11 lesions, A prominent signal for covagenase mRNA was consistently detected in the basal keratinocytes of rete ridges surrounding the neutrophilic abscesses in 10 of 11 lesions, and the expression was independent of the age of the lesion and the migratory state of the basal keratinocytes. Expression of stromelysin-1 was detected in seven of ll lesions and co-localized with collagenase. No expression of the 92-kDa gelatinase mRNA or matrilysin protein was found in the vicinity of neutrophilic accumulations or the damaged basement membrane, Urokinase-type plasminogen activator mRNA was found in basal keratinocytes in seven of nine samples, Collagenase, stromelysin-1, and urokinase-type plasminogen activator were not expressed in normal-appearing skin of patients with dermatitis herpetiformis. Out results suggest that in lesions of dermatitis herpetiformis, collagenase and stromelysin-1 map be induced in basal keratinocytes by neutrophil cytokines or by altered cell-matrix interactions through contact of keratinocytes with the matrix due to damaged basement membrane, Stromelysin-1, in particular, may contribute to formation of blisters by degrading basement membrane components.