It's a study dealing with the apical delta position in the management of peri-apical lesions. The study was carried out from the observation of root canal systems of 150 teeth mainly central, lateral incisors and canines. The study has been bounded by the conservative dentistry and oral surgery departments of the UCAD Dental Institute. It lasted from February to November 2001. We noted that the maximal height of the apical deltas comparison to the apices is 1.6 mm. So, the height of 3 mm section proposed by MEYER during the apicectomies is enough to eliminate the major part of the accessory canals.