We review the literature on comprehensive two-dimensional gas chromatography (CC x GC), emphasizing developments in the period 2003-2005. The review opens with a general introduction, the principles of the technique and the set-up of CC x CC systems. It also discusses theoretical aspects, trends in instrumentation, column combinations, and detection techniques notably mass spectrometric detection. We devote attention to a wide variety of applications and to analytical performance. (c) 2006 Elsevier Ltd. All rights reserved.