Maps are presented which show indices of organic diagenesis, and form part of a data base which includes previously published stratigraphic and structural data for assessing hydrocarbon potential in the Appalachian and structural data for assessing hydrocarbon potential in the Appalachian basin (de Witt, 1975; de Witt and others, 1975; Harris, 1975; Miller, 1975). The potential for oil and gas production in any basin depends on the presence of source beds, favorable hydrocarbon channelways, and structural and stratigraphic traps. Crucial to these factors is the level of organic diagenesis or thermal maturity within the basin. Numerous studies have shown that depth and duration of burial and geothermal gradient (time and temperature) are the chief elements producing organic diagenesis.