Decreased mucosal folding was observed by gastroscopy in 75 per cent of cases with atrophic gastritis. The average acid output per hour after “maximal” stimulation was 6.7 mEq in women and 9.1 mEq in men, which were highly significantly lower than the values found in patients with normal mucosal folding, 15.7 mEq in women and 20.7 mEq in men.