The carbonaceous organic content of the Devonian shales of the Appalachian basin is an important parameter for determining the natural-gas resources of these rocks. To calculate organic content from formation-density logs, analyses of wire-line logs from seven wells in Ohio, West Virginia, Virginia, and Kentucky were compared to laboratory core analyses. These data show that organic content computed from density logs is as reliable and as accurate as that determined from core samples. The density-log method offers the advantage of continuous sampling of the vertically heterogeneous shale section and is based on wire-line logs which are common and readily available sources of data. Plots of gamma-ray intensity versus formation density are used to determine the applicabilit of the method at a given location and to identify individual intervals where the approach may not be valid. Available data indicate that the method can be used in a large area of the western Appalachian basin.