Various histochemical techniques were performed on paraffin sections of gastric mucosa with intestinal metaplasia to distinguish mature from immature Paneth cells (PC) and to correlate their relative incidence with the degree of differentiation of metaplastic epithelium. The results show a higher incidence of immature PC in the poorly differentiated type of intestinal metaplasia than in the well-differentiated type. The identification of immature PC may be proposed as a further criterion in the evaluation of gastric dysplasia.