Fifteen heat-flow measurements are presented for eastern Arizona and neighboring areas. In the Gila Mountains of southeastern Arizona a heat flow of 1.9 HFU (the approximate average for the Basin and Range Province) is estimated from the best measurements. In the eastern part of the Safford Valley, just south of the Gila Mountains, subsurface temperature gradients were measured at one site to 1050 m. Heat-flow data from this site, considered with the reported hydrogeology and hot spring activity of the valley fill deposits, suggest complex hydrothermal phenomena in the valley. Several hundred km to the north, high heat flows (?2.5 HFU) are observed within the Mogollon Slope of the Colorado Plateau. These high heat flows, about 100 km from the southern boundary of the Colorado Plateau, are believed to result from the sources of extensive Quaternary volcanics in the region. Still farther into the interior of the Colorado Plateau the Black Mesa Basin has an estimated heat flow of 1.5--1.8 HFU and a uniform geothermal character (1 HFU=41.8mW/m2).