Studies of the Paleozoic rocks in Moravia based on abundant drillings reveal the extent of the Devonian reefs (s.l.) beneath the Carpathian Flysh Belt and Neogene foredeeps. Reef limestones (rich mainly in stromatoporoids) are restricted to the platform part of the sedimentary basin. A gradual transgression reached this area during the Givetian and Frasnian having its culmination in the Early Frasnian. Development of reef limestones in Moravia ceased at the Frasnian/Famennian boundary.