Objective To evaluate the outcome of first molar extraction in patients with crowding.Methods Totally 22 patients(8 males and 14 females) from Clinic of Orthodontics, SUN Yat-sen University School of Stomatology with crowding were cellected. The patients were aged 11 years 3 months to 26 years 8 months(mean age 16 years 6 months). All of them treated with 1 to 4 first molar extractions.Results The average duration of orthodontic treatment was 18.5 months. Normal overjet and overbite was achieved. Good funct...