The paper critically reviews the literature on the econometric issues raised by the use of generated regressors (GR) in empirical models. The economic rationale for the use of GR is considered, with examples being drawn from several macroeconomic examples, including New Classical Macroeconomic (NCM) models which postulate monetary neutrality. Various estimation methods are discussed for models which include 'surprise' or 'unexpected' terms and the strengths and weaknesses of each approach are investigated. Drawing upon the work of McAleer and McKenzie (1991b), situations where the typically inefficient two-step estimation (2SE) method will be efficient are highlighted. Problems of model misspecification and measurement errors are also investigated. An empirical section highlights some of the dangers of using uncorrected 2SE estimation results through a careful consideration of many recent attempts to test the NCM monetary neutrality hypothesis.