Calculated Bouguer gravity anomalies from the Andean orogenic belt interpreted as derived from regional gravity data to aid understanding of the lithospheric structure and tectonic evolution of the belt. These anomalies reveal lithospheric structures distributed throughout the belt, including linear and circular structures. NE-trending structures reflect sinistral transpression across the northern part of the belt, and NW-trending structures represent dextral transtension in the southern part. These results are supported by gravity-anomaly patterns that demonstrate mantle flow in a trench-parallel direction both northward and southward away from the stagnation band that is beneath the subducting Nazca slab. This mantle flow has served as an important driving force in the evolution of the Andean orogenic belt. Features of the modified tectonic model of the Andean orogenic belt are consistent with the spatial variation in and interpretation of Bouguer gravity anomalies.