Aim & Objective: To evaluate the ultra structural morphology of enamel irradiated with different parameters of the Er: YAG laser & its effect on clinical procedures involving enamel. Materials & Method: Thirty-five non-carious human premolars that were extracted for orthodontic purposes were selected &randomly divided into 7 groups. The teeth of group 1-3 were evaluated for different focal distances & the teeth of group 4-7 were evaluated for variable beam angles. When evaluating variable focal distances of 5mm, 7mm, & 10mm the beam angle was kept constant at 90° for group 1-3. When evaluating different beam angles of 30, 45, 60 & 90°, the focal distance was kept constant at 7mm for group 4-7. The laser irradiation was performed in a noncontact mode in all teeth. The teeth of each group were treated for 10 sec. The parameters that were kept constant for all groups were pulse energy of 250mJ with 15Hz frequency at very short pulse (VSP). After irradiation enamel surfaces were analyzed under ESEM. Schlagwörter: beam angle, focal distance, Er:YAG laser, apparatus, ESEM