The first "Klaus Vogel Lecture", entitled "European Tax Law, quo vadis?", was held on 25 October 2007 at the Vienna University of Economics and Business Administration (Wirtschaftsuniversität Wien). The lecture was delivered by Prof. Leif Mutén, after which Prof. Dr Jürgen Lüdicke gave his comments on the lecture. This article contains the lecture given by Prof. Mutén and the comments made by Prof. Lüdicke. Topics of the lecture include VAT, excises, tax avoidance, transfer pricing, consolidation, economic double taxation, personal allowances, and consistency. The comments consider tax treaty law and European law, and temporal limitation of ECJ judgments.