Noninvasive tests for Helicobacter pylori are important in primary care, both for initial diagnosis of H. pylori infection and for confirmation of eradication. The objective of the present study was to evaluate the effectiveness of a stool antigen test after therapy. We studied 30 patients (16 males & 14 females) infected with H. pylori at the outpatient clinic in Azady teaching hospital. After the completion of triple eradication therapy, all patients were subjected to the examination of the stool antigen test. Of the total 30 cases, there were 23 cases with negative stool Ag test after therapy. All seven cases without therapy were positive stool, Ag. The result of the stool antigen test after therapy was 76% (negative in 23 patients, false-negative in 7 patients). We concluded that a negative result on stool antigen testing after completion of therapy recognizes patients in whom the eradication of H. pylori was successful.