• E43;
  • C32
  • Fisher effect;
  • non-linearities;
  • co-integration

We argue that the empirical failure of the Fisher effect found in the literature may be due to the existence of non-linearities in the long-run relationship between interest rates and inflation. We present evidence that, for the U.S. during the 1960–2004 period, the Fisher relation presents important non-linearities. We model the long-run non-linear relationship and find that an ESTR model for the pre-Volcker era and an LSTR model for the post-Volcker era are able to control for non-linearities and constitute long-run co-integration vectors. Monte Carlo evidence produces support for the hypothesis that non-linearities may also be responsible for the less than proportional coefficients of inflation usually found in the linear specifications.