The gold standard for the diagnosis of Helicobacter pylori infection requires an endoscopic biopsy of gastric mucosa for histological examination, urease test and culture. Noninvasive serological tests are useful as a screening test for H. pylori infection. The aim of this study was to evaluate the performance of a rapid office-based serologic test, using immunochromatography ICM, and the immunoblotting for the diagnosis of H. pylori infection in Thai children. Eighty-two symptomatic children, 30 boys and 52 girls (mean age 9.2+/-3.8 years; range, 1.2-16.0 years) who had no previous treatment for H. pylori underwent upper endoscopy. Biopsies were obtained from the gastric body and antrum for histopathology and rapid urease test. Serum samples collected from all patients were tested for H. pylori IgG antibodies using ICM (Assure H. pylori Rapid Test, Genelabs Diagnostics, Singapore). Immunoblotting (HelicoBlot 2.1, Genelabs Diagnostics, Singapore) was tested in sera of 75 patients to detect antibodies to specific antigens of H. pylori. Positive H. pylori status was defined as positive for both histology and rapid urease test. Of 82 patients, 25 (30.5%) were H. pylori positive, 56 (68.3%) were H. pylori negative and one was equivocal. ICM assay yielded a positive result in 24 of the 25 H. pylori-positive patients (96.0%) and 3 of the 56 H. pylori-negative patients (5.4%). The immunoblotting yielded a positive result in all of 22 H. pylori-positive patients (100%) and in 2 of the 52 H. pylori-negative patients (3.8%). Obtained ICM's sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 96.0, 94.6, 88.9, 98.1 and 95.1%, with immunoblotting 100.0, 96.2, 91.6, 100.0, and 97.3%, respectively. The immunochromatographic and immunoblot tests are non-invasive, reliable and useful for the diagnosis of H. pylori infection in Thai children.