Multispectral imaging from the Panoramic Camera (Pancam) instruments on the Mars Exploration Rovers (MERs) Spirit and Opportunity has provided important new insights about the geology and geologic history of the rover landing sites and traverse locations in Gusev crater and Meridiani Planum. Pancam observations from near-UV to near-infrared (NIR) wavelengths provide limited compositional and mineralogic constraints on the presence, abundance, and physical properties of ferric- and ferrous-iron–bearing minerals in rocks, soils, and dust at both sites. High-resolution and stereo morphologic observations have also helped to infer some aspects of the composition of these materials at both sites. Perhaps most importantly, Pancam observations were often efficiently and effectively used to discover and select the relatively small number of places where in situ measurements were performed by the rover instruments, thus supporting and enabling the much more quantitative mineralogic discoveries made using elemental chemistry and mineralogy data. This chapter summarizes the major compositionally and mineralogically relevant results at Gusev and Meridiani derived from Pancam observations. Classes of materials encountered in Gusev crater include outcrop rocks, float rocks, cobbles, clasts, soils, dust, rock grindings, rock coatings, windblown drift deposits, and exhumed whitish/yellowish sulfur- and silica-rich soils. Materials studied in Meridiani Planum include sedimentary outcrop rocks, rock rinds, fracture fills, hematite spherules, cobbles, rock fragments, meteorites, soils, and windblown drift deposits. This chapter also previews the results of a number of coordinated observations between Pancam and other rover-based and Mars-orbital instruments that were designed to provide complementary new information and constraints on the mineralogy and physical properties of Martian surface materials.