Abstract Over the last decade, a new exploration frontier has opened up in Patagonia, Argentina, for gold mineralization. Important deposits, such as Cerro Vanguardia and Esquel, were discovered during this period. Despite these discoveries, basic geologic information for the vast Patagonia territory is still markedly scarce for generating targets for mineral exploration. In such a scenario, in which a prevailing arid climate and sparse vegetation often leave favorable bedrock exposed, multispectral satellite remote sensing is playing an important role in gold prospecting. This paper presents the results of a remote sensing project developed over northern Patagonia with the purpose of mapping potential areas of epithermal gold mineralization. A reconnaissance program using Landsat Thematic Mapper (TM) imagery to search for favorable targets on a regional scale was carried out, focusing on the mapping of possible hydrothermal alteration zones. The effectiveness of the results is evidenced by the fact that the majority of the hydrothermally altered targets pinpointed using Landsat TM showed anomalously high gold grades after follow-up geochemical analysis. Within the scenes analyzed, the region of Los Menucos stood out as having a high number of conspicuous altered areas carrying gold values greater than 0.1 g/t (some greater than 1 g/t). With the launch of Terra in 1999, carrying onboard the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), the Los Menucos region was further investigated to map alteration. A suite of advanced image processing methods was applied to the data, with the purpose of detecting and identifying key alteration minerals. The results accomplished in the Los Menucos region with Landsat TM and ASTER data demonstrate the capabilities of multispectral remote sensing for alteration mapping in frontier exploration regions, ranging from regional scale to district and deposit scales.