Arapid colorimetric technique for determination of active iodine in soilsis recommended in this paper? this method, based on the reaction betweentetrabase and chloramine T, has the determination range of 0.01-1ug/25mland is characterized by simplicity and high efficiency with 50-60 determin-ations made per man-day.The possibility of using iodine as a pathfinder element in geothermalexploration has been investigated. With the mentioned colorimetrie methoda-bove, the authors have determined 193 surface soil samples along11 profilesover the Yangbajing geothermel field in Tibet, covering an area of 25 km2.From the data obtained, a map showing the distribution of extensive andintense iodine anomalies is drawn. The distribution of iodine anomalies coin-cides quite well with that of resistivity or soil mercury anomalies, and is inconformity with the underground geothermal reservoir. This implies thatIodine is likely to be an important pathfinder element in geothermal explora-tion.