The Authors experimented the use of "modified" straight wire orthodontic appliance on an experimental group of 15 patients who present orthodontic problems with skeletal I, II and III class. Treatment difficulties and results were compared with those obtained in a control treated by the Tweed technique. The Straight Wire appliance proved to be able to reduce, especially in class III problems, treatment's length. Besides, the easiness of learning and performing the orthodontic straight wire technique was evaluated. The Authors found that the main difficult for the Tweed technique is the necessity of a good manual ability, while the most important problem using the straight wire technique is the correct positioning of the brackets.