The purpose of this study was to investigate the performance of Er:YAG laser when used with a tip curved at 100 o in retrograde cavity preparation. Ten extracted single-rooted human teeth, prepared and obturated using the lateral condensation method, were resected 3 mm from the apex. Retrograde cavities were prepared using either an Er:YAG laser or an ultrasonic unit. There was no significant difference between the two methods with respect to working time and postoperative increase in the root canal area. In conclusion, retrograde cavity preparation performed with the Er:YAG laser is as effective as with the ultrasonic retro-tip.