Slovenia is characterized by a complex tectonic setting owing to its geographic position. Various rock types occur, and they belong to the igneous, metamorphic or sedimentary group. Among the latter, limestone and dolomite predominate ranging in age from Devonian to Tertiary, and they are accompanied by sandstone, conglomerate, marl and other clastic and pyroclastic rocks. During the five-year programme we studied petrography of all above mentioned rocks (some thousand samples), their genesis, diagenetic and metamorphic processes, sedimentary environments and microfacies (shallow-water, deep-water, fresh-water etc.). Our research was focused on igneous and metamorphic formations of the mountains of Pohorje and Strojna, Permian and Triassic carbonate rocks in Western Slovenia, limestones at the Cretaceous/Tertiary boundary, Paleogene limestones in Karst, Tertiary clastic sediments and pyroclastic rocks of Kozjansko and Goričko, flysch sedimentary rocks of the Primorska region, cave sediments of Potočka zijalka, and recent sediments of the lake of Bled. Rock recognition and other data obtained are the basis for numerous activities and research related to economy, environment protection and space planning of Slovenia: for elaboration of various geological and thematic maps (i.e. natural resources, hydrogeology, geochemistry), for the study of underground geological structures by deep wells, the study of earthquakes and other natural catastrophes, estimation and classification of mineral (mainly non-metal) ore deposits, the study of environment pollution and for extensive geological information system. Research, carried out in the programme framework has international character, too. Many works are related to the areas of our neighboring countries, and were partially accomplished as bilateral cooperation projects. The programme is also important for maintaining a quality level in sedimentology and petrology in comparison with the World. Our knowledge is transferred to the education process, too.