The recent Si supply shortage has provided a foretaste of what might occur when a photovoltaic technology becomes materials-supply constrained. Non-silicon technologies, involving some of the least abundant materials in the earth's crust, have even more fundamental problems with material availability. For both Te and Se, Cu anode slimes produced during Cu electrolytic refining provide the present major supply stream. The availability of material from such slimes is reassessed using recent data and shown to be more limited than earlier estimates. Copyright © 2006 John Wiley & Sons, Ltd.