At present, inspection and maintenance operations on various types of pipelines, structures, and others are carried out manually by human operators. Such operations are often performed, in general, under adverse environments such as high places and narrow areas. In addition, fire fighters in blazing high-rise buildings may be subjected to dangers involving high places and fires. Moreover, the robotization of grinding work in factories, for example, require a large number of empirical technologies. In order to mechanize tasks under such adverse environments and under special working conditions, research has been conducted, including studies of mobile mechanisms on inner walls and outer walls of piping, on wall surfaces of structures, etc. or studies of force control methods. Under these circumstances, this issue will be specialized in technical progress of various types of maintenance robots. First, a navigation system of a wind quantity inspection robot using a fuzzy neural network will be discussed by Messrs. Fukuda and Abe. Next, a report will be given by Messrs. Ishikawa and Shiire on the mechanism and functions of a pile recovery robot for large-diameter pipes, with a view to carrying out cleaning work inside cooling water pipes of electric power generation plants, as well as on its field testing. Furthermore, Messrs. Kawaguchi and Yoshida will be asked to report on the mechanism of an inspection robot for use on the inner surfaces of gas piping buried in the ground. In addition, a discussion will be carried out by Messrs. Naruse and Takada on the mechanism and fire extinguishing capability of a hybrid robot system for use in combatting fires in high-rise buildings. Moreover, Messrs. Ozaki and Jinno will be discussing the mechanism and force control system of a grinding robot. In addition, a discussion will be carried out by Messrs. Hosokai and Hara regarding the motion function of a piping inspection robot having a lazy tong mechanism and also regarding its piping test results. Finally, Messrs. Amano and Kakikura will be called upon to give a discussion concerning a robot for carrying out exfoliation of finishing materials on the outer walls of structures and its exfoliation. In closing, it is hoped that this special issue will be of some help in the future when such maintenance robots are developed.