In twelve patients on chronic haemodialysis, a relationship was established between gastric acid secretion on the one hand, and certain parameters of calcium metabolism on the other hand: in a multifactorial statistical analysis, plasma calcium before dialysis (p less than 0,05), plasma parathormone levels before dialysis (p less than 0,05) and plasma calcitonin before dialysis (p less than 0,05) were variable explicatives of basal gastric acid secretion according to a direct relationship, whilst plasma calcium (p less than 0,05) was the only explicative variable of maximal gastric acid secretion after pentagastrin, with an inverse relationship. These preliminary results suggest that gastric acid secretion in the haemodialysis patient must be interpreted in the light of the state of calcium metabolism. Thus hypocalcaemia may be accompanied by decreased basal acid secretion and by contrast by an increased maximal acid secretion. These results require confirmation in a larger number of patients.