Statement of Problem: β Thalassemia is a hereditary hematologic disease with the manifestation of sever dental problems in affected patients.Purpose: The aim of this study was to examine dental arch dimentions and occlusion in patients with β-thalassemia in Children Hospital of Tabriz in 2005.Materials and Method: The sample consisted of patients suffering from β-thalassemia with mean age of 14.9±3.2 and an unaffected control group with mean age of 13.5±3.9. Impressions were made and measurements obtained with a Caliper. Over jet, Overbite and molar relation were recorded clinically. Statistical analysis was then performed using the two-tailed t-test and significance was set at p<0.05.Results: In mandibular arch, when compared with thalassemic patients, healthy subjects showed a significantly larger incisor width, larger arch depth, and larger left and right anterior arch lengths. In the maxillary arch, statistically significant differences were found in mean incisor width, arch depth, intermolar width and left anterior arch length. The canine widths, premolar width, left and right posterior arch length and curve of Spee of both arches showed no statistically significant differences between the two groups.Conclusion: When compared to unaffected subjects, patients with β-thalassemia exhibited a narrower maxilla, a shorter maxilla and mandible, smaller incisor width for the maxillary and mandibular arches. Key words: Thalassemia major, Arch depth, Occlusion, Jaw dimension