The course gives both a rigorous and applied introduction to modern econometrics. How regression makes sense: What is the justification for linear regressions in the first place? Theory-based regression, conditional expectation function, prediction and causal model. The algebra of least squares. Classical assumptions and large sample results. Specification issues (omitted variables and multicollinearity). Generalized Least Squares. Endogeneity: Reasons and solutions. Instrumental Variables. Generalized Method of Moments, Two-Stage Least Squares. The course tries to balance intuitive understanding with rigorous treatment. The course "Quantitative Methods in Economics and Business" (or comparable) is a prerequisite.