This text provides an examination of the key macroeconomic theories which underpin fixed asset investment. It would make ideal reading for an intermediate level macroeconomics course or a module on fixed asset investment taking an applied macroeconomic perspective. Table of Contents Section I Introduction: introduction an overview of concepts and approaches. Section II Theoretical issues: the intellectual ancestors - Irving Fisher and Maynard Keynes accelerator theory Jorgenson's model of investment the limitations of Jorgenson's model putty clay models of investment adjustment costs and q theory uncertainty and investement post Keynesian analysis of investment. Section III testing the theories: comparing Jorgenson's model and accelerator theory - evidence from the UK uncertainty in competing models of investment - evidence from the USA. Section IV Empirical applicaitons of investment principles: computing investment in the new economy - US evidence investment and development - a cross sectional analysis residential investment - bubbles and crashes in the UK housing market 1980-99. Section V Conclusion: concluding remarks bibliography statistical appendix - some basic econometric techniques