Chemical and isotopic data of thermal springs and wells indicate that some thermal water circuits in central and south Vietnam can reach temperatures of geothermal interest (150-200 degrees C) in zones of normal-to-slightly anomalous thermal gradients, The low gas content and the low CO2 and H2S concentrations suggest that there is no contribution from a magmatic source. The geothermometry results indicate that the geothermal resources in south and central Vietnam are of medium enthalpy. These results confirm those of previous geochemical surveys and indicate that the most promising geothermal sites in Vietnam are Le Thuy, south of Dong Hoi and Mo Duc near Quang Nghai.