Abstract The geologic history of Alaska records evidence of multiple episodes of extension, subduction, are-continent collision, accretion, and orogenic and anorogenic magmatism. Porphry copper formation is episodic, having occurred at ten intervals within the Silurian to Quaternary periods. Although magmatism spans Archean(?) or Early Proterozoic through Cenozoic time, all known porphry copper occurences are Silurian and younger, a peak of mineralizing activity being the Cretaceous period. Porphyry copper prospects and deposits in Alaska occur in association with intrusions or intrusive complexes containing diorite to granodiorite and volcanic equivalents and commonly monzonite ± granite. Porphyry copper formation is commonly coincident with intrusive episodes of are magmatism, characterized by a greater mantle or oceanic component and hence by more primitive strontium initial ratios. In contrast, magmatic belts that incorporate a significant crustal component, as shown by elevated strontium initial ratios and common lead isotope ratios, may host porphyry copper occurrences only rarely. Porphyry copper occurrences in Alaska exhibit propylitic, phyllie, and less commonly, argillic and potassic alteration. Complete zonal alteration assemblages are rarely recognized at individual porphyry copper occurrences. Mineralization is hosted as veinlets, veins, and disseminations, with pyrite, chalcopyrite, and molybdenite making up the most commonly reported sulfides. Wall-rock skarn hosts significant additional copper resources in selected deposits. A step-wise palinspastic reconstruction shows that many porphyry copper occurrances formed near the paleocontinental margin or off-margin, as clusters, or as linear belts which subparalleled the paleotrench. Exploration for porphyry copper occurrences in Alaska is incomplete, and new discoveries are probable.