[en] In May 1976, a meeting of Tokamak physicists was held in order to discuss what is known about impurities in tokamaks, what one should be able to learn from planned experiments, and what issues remain unaddressed by present or future programs. Out of this meeting have come detailed reports from each of the Tokamak laboratories and this overview report written by Tony Hsu and containing the laboratory reports as an appendix. This report is intended to provide background and perspective for further discussion as well as detailed information on impurities in Tokamaks. Since the spring of 1976, PLT experiments have focused even more attention on impurities. As this report goes to press, the effects of neutral beam heating on impurity generation and the effects of impurities on neutral beam penetration and heating are of the greatest importance to the Tokamak program. Near term experiments on PLT are expected to give preliminary answers to these questions