Over 500 bulk analyses are available in the literature about the intermediate volcanic rocks of the Tokaj Mountains, NE Hungary. Following careful selection, about 400 samples were chosen for detailed sta-tistical analysis in order to answer some open questions concerning petrologic circumstances of the rather complex magmatic series. The most fundamental aim was to identify the essential magmatic and post-magmatic processes, one can define using the geochemical data. Based on these processes we compare the current petrographic classification scheme to the geochemical data based group structure of the samples. The final question studied concerns spatial appearance of the identified petrographic processes and the samples groups defined using geochemical data. Results of a sequence of traditional statistical methods (factor, clus-ter and discriminant function analyses) suggest that beside igneous differentiation different post-magmatic processes significantly determine bulk composition of the studied intermediate rocks. Due essentially to the complex alteration history, rock classes were defined using petrographic observations previously, hardly meet the group structure can be defined using geochemical data. In fact, trachyte is not an original igneous rock type; rather it is regarded as intensively metasomatised dacite and andesite. Interpolated maps of the identified magmatic and post-magmatic processes (factors) clearly mimic the spatial pattern of the known volcanic and sub-volcanic centers suggesting that alteration coincides to late dacitic activity.