Despite the importance of predicting investment expenditures for regional economic forecasting and policy simulation, little has been published on predicting regional investment expenditures. The primary reason is the lack of data on regional investment and capital stocks. Using two constructed investment data sets, this paper specifies and econometrically estimates stock adjustment equations of residential and nonresidential investment for the fifty states plus Washington, D.C. Unique aspects of the approach include maximum use of United States and regional data, and pooled estimation. The estimated pooled equations provide satisfactory historical fits to investment for most states. Also, the paper presents out-of-sample forecasts and simulated investment responses to an exogenous production increase.