This paper documents several advantages associated with using state level consumption data to examine consumption behavior and especially to estimate the Intertemporal Elasticity of Substitution (IES). In contrast to the results of Hall (1988) and Campbell and Mankiw (1989), we provide substantial evidence indicating that the IES is significantly different from zero and probably close to one. Since the overidentifying restrictions of the standard Euler equation are generally rejected, we use these data to explore the nature of these rejections and evaluate an alternative specification of consumer behavior proposed by Campbell and Mankiw (1987, 1989, 1990). We take special care of examining the robustness of our results with respect to problems caused by the mismeasurement of the interest rate. In particular, we identify a common time component in expected consumption growth across states which, under the specifications of the theory, should reflect real interest rate movements. We find that the common time component closely matches the expected real return on Treasury bills as should be expected if the IES is different from zero and if the T-bill rate is an appropriate measure of interest rates.