August 21, 2004 Counterfeiting poses a significant public policy issue because of the important role that paper money plays in Canada's payments system. Yet the threat of counterfeiting in all economies has increased markedly in the past decade as a result of technological advances to photocopiers and computer printers. An appropriate pubic policy response is thus necessary to maintain the public's continued confidence in the national currency. To assess the threat from counterfeiting, including possible loss of confidence in the currency, estimating the stock of counterfeits circulating is necessary. In this article, Chant proposes a composite method of detecting counterfeits as an effective alternative to existing methods and offers estimates of the extent of counterfeiting Canadian currency for 2001. An Addendum to the article summarizes Chant's methods and updates the calculations to 2003.