Carbon isotope ratios of graphites were studied in carbonate-free metasediments of the Tauern Window and the Köszeg-Rechnitz Windows of eastern Austria and western Hungary that belong to the Alpine Bündnerschiefer series. The stable carbon isotopic compositions of the graphites range from about -22 ‰ to -12 ‰ and show systematic regional distribution patterns. Variations in δ13C are explained as mixing of anormal marine component (-22 ‰) and a detrital carbonaceous component (-12 ‰). The detrital component is similar to the carbonaceous matter of black pebbles of conglomerate bodies that occur in the same sedimentary sequence. Based on the δ13C values, a distinction can be made between sediments deposited in the southermost part of the Penninic ocean basin and sediments deposited more to the north. The results are used for possible sedimentary facies correlations between rocks in the Alpine Penninic windows.