The incidence of parietal cell antibodies (P.C.A.) in patients with various diseases was investigated by complement fixation test (C.F.T.). The relationship between the incidence of P.C.A. and clinical and pathological findings was also investigated. The incidence of P.C.A. with simple atrophic gastritis was 34.8% in total cases, 29.0% in male and 48.1% in female, respectively. The difference between the sexes was statistically significant (p less than 0.05). The incidence of P.C.A. in superficial gastritis was 37.5%, showing the same incidence as atrophic gastritis. The difference between the two groups was not statistically significant (p less than 0.05). The incidence in patients with hypo- and hyperactivity was 43.0% and 11.8%, respectively. The difference was statistically significant, but that between hypo- and normoacidity was not significant (p less than 0.05). The author postulated the conclusion that the superficial gastritis could be included in the category of atrophic gastritis. The dissociation of correlation of titer of C.F.T. with acidity and histological findings was found. The correlation was more significantly observed with acidity than with histological findings. The relatively high incidences of P.C.A. were noted in patients with peptic ulcer, gastric carcinoma and chronic thyroiditis. The incidence of P.C.A. in other diseases showed the nearly equal incidence to that of other investigators. Three cases of postgastrectomy patients were noted, in which the P.C.A. disappeared four to six months after total or subtotal gastrectomy.