Many of the problems that have occurred in solar systems show the need for careful maintenance. Experience with a large variety of solar systems, especially those in the HUD Solar Residential Demonstration Program, has shown that regular inspection arid maintenance can often help in avoiding many of the serious problems or in decreasing the damage and loss resulting from them. In this paper are discussed questions relating to maintenance of solar systems and the types of problems that can be prevented or alleviated by proper maintenance, as well as what needs to be done for maintenance in different kinds of solar systems, including liquid-based and air-based systems and both active and passive solar systems.