Identifying and quantifying chemical groups is an important task in sample analysis.Comprehensive two-dimensional gas chromatography (GC × GC) provides increased separation capacity and multi-dimensional structure-retention relationships which can be exploited for improved chemical group analyses.Three computer-based methods for extracting and visualizing chemical groups are described here.The first method, complete linkage with principal component analysis (PCA), can be used with scalar GC × GC data such as produced by a flame ionization detector (FID).This method groups chemical peaks into "clusters" based on retention times.The retention times of peaks in a cluster are transformed so that chemical groups, which commonly appear as striated bands in GC × GC data, can be recognized.Peaks clustered with this method can be assigned a common group name and colorized as a group for visualization.The chemical grou p ean be quantified as the sum of the quantities of the individual peaks in the cluster.