Comprehensive two-dimensional gas chromatography (GCxGC) provides a true orthogonal separation system. It is explained and demonstrated that it generates a peak capacity that is approximately equal to the product of the peak capacities of the two individual separation systems. The resulting peaks are ordered in a two-dimensional plane in bands of compounds with the same characteristics. Quantitation of the separated (groups of) components is fundamentally not different from one-dimensional gas chromatography, but the sensitivity is far better and true baseline is always available. The two co-ordinates of each peak in the plane make the identification more reliable. Instrumental considerations of GCxGC are discussed. The three designs of contemporary GCxGC systems are presented and compared. Although the technique is still very young, a number of applications on complex samples as petroleum and environmental samples have already been reported. Finally, the future perspectives of GCxGC are discussed. Copyright (C) 1999 Elsevier Science B.V.