Abstract. The present study relates to the discrimination of opium poppy fields in northern Thailand using Landsat TM multispectral imageries. In several countries in Asia, a high priority is given to drug control policies and to the eradication of opium poppy cultivation. This is the case in Thailand, where the government is engaged in a permanent inventory of shifting cultivation practices in opium producing areas, especially in the Golden Triangle. The study area is included within 1 TM frame for which two dates are available, in 1993 and 1995. Both have been geometrically corrected in order to be superimposed. Various methods have been tested to enhance the imageries and to facilitate the visual interpretation. The imageries have been field checked both aerially and on the ground. The results are technically interesting for the detection and the eradication of these illicit crops. The discussion indicates the level of accuracy that may be obtained.