We have already reported the promising ability of the Er: YAG laser to ablate subgingival calculus in vitro. The purpose of this study was to examine the features of the laser-scaled root surface in comparison with the ultrasonic scaling. Twenty-four periodontally involved human extracted teeth with a band of subgingival calculus were used. The teeth were randomly divided into two groups for laser scaling and ultrasonic scaling. An Er: YAG Laser ML22 (Erwin®;HOYA Co. and J. Morita Mfg. Co., Japan) and an ultrasonic scaler (SOLFY®; J. Morita Mfg. Co., Japan) were used in this study. Laser scaling was performed carefully in the contact and non-contact mode at the energy output of 40mJ/pulse (14.2J/cm2/pulse) and 10 pps under water spray, keeping the contact probe obliquely to the root surface. Ultrasonic scaling was performed at power 4 which is a standard power for clinical use. The features of the scaled site were observed by optical microscope or scanning electron microscope (SEM). The laser scaling was capable of removing subgingival calculus effectively. The laser-scaled area showed a slightly rough appearance macroscopically. Histologically, a thin thermally-damaged layer was observed on the lased root surface. The SEM examination of the lased root surface revealed a characteristic microroughness. This study suggests that the Er: YAG laser could be clinically applicable for the debridement of the periodontally diseased root surfaces. Further studies are required on the evaluation of the attachment of the periodontal tissue to the lased root surface and the necessity of the treatment for removing the superficial layer of the lased root surface.