Oolitic and oncoidal rocks, microfacies, depositional environments and their stratigraphic ranges in Sloveniaare subjects of this article. Various types of calcareous ooids are present in the Upper Carboniferous, Permian andTertiary (Paleocene and Miocene) beds and specially at many levels in an up to 6000 meters thick statigraphic successionof the Mesozoic age. Sedimentological investigations have been carried out specially in the Triassic andJurassic beds. The ooids occurring in the shallow-water and intertidal carbonate environment have been groupedinto seven types and oncoids into four types. Oncoids are rather more aboundant in Carnian and Norian/Rhaetianage. Late dolomitization of some oolitic beds is next to cementation the main diagenetic feature.