The talk will present the instrumental variables (IV) regression estimator, a key tool for the estimation of relationships incorporating endogeneity/two-way causality or measurement error, focusing on the Baum/Schaffer/Stillman ivreg2 package and Stata 10’s new ivregress command. The IV or two-stage least squares estimator is a special case of a Generalized Method of Moments (GMM) estimator. GMM techniques are appropriate when non-i.i.d. disturbances are encountered. We will discuss tests of overidentification, weak instruments, endogeneity/exogeneity and recently developed tools for testing functional form specification (ivreset) and autocorrelation in the IV context (ivactest).