In 1984 and 1985, as part of its Alaskan critical and strategic minerals project, the Bureau of Mines mapped and sampled reported tin occurrences associated with the Ohio Creek Pluton, in the central Alaska range, south-central Alaska. The pluton is a composite intrusion with a core of moderately coarse-grained biotite granite and an outer zone of finer grained leucocratic muscovite granite. Tin mineralization, associated with silver, base metal, and tungsten values, occurs within the muscovite granite as cassiterite (sNO2) within both quartz-muscovite greisen and arsenopyrite veins. Silver occurs within argentiferous galena and argentite (ag2s); tungsten is present in the mn-rich wolframite mineral huebnerite (mnwo4). Samples of arsenopyrite veins average 0.7 pct sn over 0.5 Ft, whereas samples of muscovite or quartz- muscovite greisen average 0.17 pct sn over 1.0 Ft. Metallurgical testing of three large samples of tin-mineralized greisen showed tin recoveries of 27 to 64 pct in table concentrates; respective grades of concentrates range from 39.4 to 72.1 pct sn. A low-grade (0.06 pct sn) zone near the pluton's upper contact containing numerous relatively closely spaced greisen-bordered arsenopyrite veins is inferred to contain a resource of approximately 1,250,000 lb sn.