Background: Serial extraction (SE) or guidance of eruption is reversed for treatment of severe tooth-size arch -size discrepancies, where space deficiency is more than 10 mm. It seems necessary to have sufficient information on the types of malocclusion and hereditary crowding. Of course, most cases of 5 to 9 mm space deficiency need serial extraction after through diagnosis and treatment planning in order to preserve facial esthetics and the integrity of the supporting soft tissue. It is necessary to have a through understanding of the growth and development with all its ramifications, and it is also essential to be aware of the occlusion of dentition, with its relationship to the craniofacial structures and its function. This study was performed to categorize the malocclusion to types and to assess the need for hereditary crowding and serial extraction among 7-9 year old children.Materials and Method: After providing questionnaires, 3776 children with an age range of 7-9 years were randomly examined for occlusion condition and crowding.Results: Different malocclusions were obtained to be as follows: 30.5% normal class I occlusion; 47.4% Cl.I malocclusion; 13.7% Cl.II Div.1 (male/ female ratio was 3:2); 1% Cl.II Div.2 malocclusion (male/ female ratio was 3:1) and 2.1% Cl.III malocclusion. Conclusion: Among the students, 47.9% had crowding problems and 14.7% had class I malocclusion which were observed in girls to be 17.3% as compared to boys (12.1%). Keywords: Serial extraction, Space deficiency, Hereditary crowding.