This issue of ECS Transactions contains papers on electrochemical aspects of concentrating and extracting base, precious and light metals from their ores and secondary materials, and associated energy and environmental considerations. Both fundamental and applied work is covered with emphasis on recent progress in: (1) mineral flotation, (2) hydrometallurgy, (3) electrowinning and refining, (4) environmental technologies associated with mineral and metal processing, (5) electrochemical methods for secondary metal production, and (6) recovery of metals from wastes.