Using ELISA, a specific and sensitive system that detects serum immunoglobulin G antibodies against all soluble antigens of Helicobacter pylori (Hp) has been developed. This system is used at three different concentrations of Hp antigens coated on the solid phase of the ELISA. Anti-Hp antibodies were judged positive when the difference in the ELISA values between high and middle or middle and low concentrations of antigen were over the specific values. For the ELISA system, called the three point antigen method, sensitivity and specificity of urease activity were 86.9% and 70.8%, respectively. Positive rate for antibodies to serum Helicobacter pylori in dyspeptic patients was higher than that in healthy subjects.