Twenty-six new estimates of heat flow are calculated for the Albuquerque-Belen Basin and the basins of the southern Rio Grande rift in New Mexico. From these and previous data the following heat flow patterns may be suggested. The regional or ''background'' heat flow in the Albuquerque-Belen Basin is ~77 mW m-2. There is also a NE-SW trend of higher heat flow (92-110 mW m-2) across the region. In the southern Rio Grande rift, between Socorro and Las Cruces, the regional heat flow appears to be ~95 mW m-2. In this region there are also higher heat flows (117-135 mW m-2) at widely scattered sites. South of Las Cruces, near the international border between Mexico and the United States, preliminary and perhaps suspect data suggest the possibility of a transition to the intermediate heat flows previously estimated at sites throughout much of northeastern Chihuahua, Mexico. Regional heat flow values in the Albuquerque-Belen Basin, and in the basins of the southern Rio Grande rift, are consistent with, but do not constrain, simple models of crustal thinning. Higher heat flows in these two areas are thought to be caused by hydrothermal fluids (largely groundwaters but possibly magma in some areas) transporting heat upward along crustal fracture zones.