August 11, 1996 This article compares different measures of real short-term interest rates for Canada over the period from 1956 to 1995. A new measure for the expected real interest rate is constructed using a proxy for inflation expectations that is based on the properties of past inflation. The history of inflation in Canada suggests that the characteristics of inflation have changed considerably over time. Past inflation can be characterized by three different types of behaviour: an environment in which average inflation is low and shocks to inflation have only temporary effects; an environment of moderate inflation with more persistent disturbances; and an environment of drifting inflation in which shocks have permanent effects on the level of inflation. The proxy for inflation expectations uses a statistical model, called a Markov Switching Model, to take account of changes in the behaviour of inflation over time. It is found that uncertainty about the changing characteristics of inflation behaviour leads to uncertainty about estimates of inflation expectations and thus about measures of real interest rates. Target ranges for keeping inflation low should help reduce the uncertainty about inflation behaviour. The behaviour of inflation and interest rates suggests that the credibility of the Bank of Canada's inflation-control objectives is growing. This should reduce inflation uncertainty and lead to lower nominal interest rates over time.