ABSTRACT Four Upper Triassic patch-reefs exposed in the Northern Limestone Alps of the Salzburg area of Austria were subjected to detailed study. Especial emphasis was placed on facies development and paleoecologic zonation of the reef complexes. The Adnet Reef structure grew directly on a carbonate platform in a shallow water carbonate setting; the Rötelwand and Feichtenstein Reef complexes grew out of the Kössen Basin in two distinct stages: 1. a deeper water mud-mound stage and 2. a shallow water reef stage; whereas, the Gruber Reef, which also developed within the Kössen Basin, only shows a deeper water mud-mound stage, since a shallow water phase did not develop at this location. The shallow water reef stages of the reef complexes display a lateral facies zonation consisting of five different facies units: 1. coral-sponge facies of the central reef areas, 2. oncolitic facies of the exposed upper reef-slopes within zones of highest water energy, 3. algal-foraminiferal facies of the exposed lower reef-slopes, and as the foundation of the Adnet Reef structure, 4. reef detritus-mud facies of the leeward and deepest portions of the reef-$Iopes, where reefal components interfinger with Kössen basinal sediments, and 5. terrigenous-mud facies of the basin proper. The Rötelwand and Feichtenstein Reef complexes display a linear facies zonation, while the Adnet Reef Structure displays a circular and somewhat patchy facies zonation. Organism communities forming the reef biota are characterized by the association of various reef framebuilders and their epi- and endobionts. The compositional relationships of the various patch-reefs, their gross morphology, paleoecologic setting, and depositional environments have been studied in detail. This study has demonstrated that calcareous algae, various microproblematica, and foraminifers show very distinct distributional patterns within the reef complexes, and can be used as facies indicators as well as differentiating different biotopes within the central reef areas.