The Viking primary mission (June 20 to November 15, 1976) yielded approximately 50 images of Phobos and Deimos. These pictures completed the surface coverage of Phobos begun by Mariner 9 in 1971--1972 and extended the coverage of Deimos. The effective resolution of the Viking images exceeds that obtained by Mariner 9 for two main reasons: improved camera performance and closer encounter distances. The improved resolutions revealed a number of unexpected surface features such as linear chains of irregular craters and elongated grooves and striations. The Viking coverage has provided the first high-resolution color information on the surfaces of the two satellites and has extended the phase angle coverage to 125¿. Additionally, a number of images of the satellites were obtained against star backgrounds to refine further the ephemerides.