Color changes in conodonts are established thermal indices that have been related to the thermal window for hydrocarbon generation and preservation and that also have value for targeting mineralization potential. Conodont color-alteration values from 141 localities in Arizona appear to characterize the thermal maturation of the major Paleozoic outcrop areas in the state. Paleozoic rocks in the Colorado Plateau, in part of the belt of faulted plateau-like rocks bordering the plateau, and in a small area (from 31°20^prime to 31°44^primeN and from 110°00^prime to 110°40^primeW) in southeast Arizona have thermal potential for oil. Paleozoic rocks in the same areas as well as in the Pedregosa basin (southeasternmost Arizona) have thermal potential for gas. f these areas, southeast Arizona appears to have the best hydrocarbon potential because of the association of possible source beds and favorable thermal-maturation levels.