A GEOSCAN MkII aerial multispectral scanner was used to acquire nighttime thermal infrared (TIR) imagery over an area extending from southern Lake Tarawera to northern Reporoa as part of a surface geothermal feature mapping and monitoring project. This data, which covers a 100 km(2) area at a ground spatial resolution of about 3 m, was obtained in six contiguous channels spanning the wavelength range 8.4-11.6 mu m. Results from the preliminary analysis of band 20 (9.17 mu m) are presented here. All known major geothermal features, which include hot springs and streams, hot ground and thermal seeps into lakes, were detected and accurately mapped on imagery rectified to the New Zealand Map Grid. In addition, several previously unreported thermal features were identified. The imagery clearly showed that the abundant surface activity at Waiotapu occurs along lineations, convincing evidence of structural control of permeability. A large hot spring, which has appeared on the north shore of Frying Pan Lake (Waimangu) since the last lake survey, was identified, demonstrating the usefulness of the TIR method for monitoring temporal changes in surface manifestations. Surface temperatures were estimated from empirically calibrated imagery and results for two Waimangu thermal crater lakes agree with measured values to within 1-2 degrees C.