In order to extract new information about contaminants and their distribution patterns in a regional groundwater contamination from existing large databases, a three-step investigation strategy was developed and it was applied to the regional groundwater contamination in Bitterfeld-Wolfen (Saxony-Anhalt, Germany). In the first step, data from different groundwater monitoring programs were consolidated and data quality was evaluated. In the second step, substance-specific generalised contamination criteria (detection frequencies and average detected concentrations) were determined for organic substances. The two contamination criteria were then ranked with different methods (contamination profiles, Hasse diagram technique, cluster analysis). In this way, the local and the regional relevance of each substance under study was identified. Furthermore, regional representative substances were determined for the groundwater monitoring program (among others tetrachloroethene, vinyl chloride, monochlorobenzene, alpha-HCH). On the basis of the ranking results, three regional relevant parameter sets were selected for the statistical pattern recognition, the third investigation step. They were analysed with correlation analysis, principle component analysis and cluster analysis. In each of the three parameter sets it was possible to detect distinct contamination factors for the regional groundwater contamination. Moreover it was possible to visualise spatial patterns by means of cluster analysis. This three-step procedure does not only increase the understanding of the composition of the contamination under study, but it also provides starting points for the optimisation of the groundwater monitoring program in Bitterfeld-Wolfen. The methodological strategy is applicable to other regional groundwater contamination sites, which currently occur on many former industrial sites.