OBJECTIVE To study the effect of anterior plate fixation on the treatment of middle and lower thirds fractures of humerus and the possibility of operating without injuring the radial nerve. METHODS Forty-nine patients with the middle and lower thirds fractures of the humerus were treated with anterior plate fixation from March 1998 to December 2002. Of the 49 patients, 27 were with new fractures, 12 with old fractures, and 10 with nonunion fractures. According to AO classification, of the 49 patients, there were 19 type A, 14 type B1, 9 type B2, 5 type B3, 2 type C1. Thirty-seven patients had closed fractures and 12 had open fractures. Of the 12 patients, 8 were type Gustilo I , 4 were type Gustilo I . Four out of the 49 patients were associated with radial nerve palsy. All patients were treated with anterior plate fixation through the anterior approach to the humerus. The radial nerves injured were explored. RESULTS Of the 49 patients, 48 were followed up 6 to 48 months (28.7 months on average). All fractures were healed within 3 to 9 months(4.7 months on average). Fixed plates of 37 patients out of the 49 were removed. No iatrogenic radial nerve injury occurred in the 82 times of the operations among the 49 patients. CONCLUSION The treatment of middle and lower thirds fractures of humerus by anterior plate fixation through the anterior approach to the humerus does not interfere with the fracture healing and can prevent the iatrogenic radial nerve injury.