The Korucu-Dugla study area (225 km(2)) located in western Turkey was selected for the application of Landsat Thematic Mapper (TM) data to geological studies. A wide variety of image processing techniques including; principal component analysis (PC), intensity-saturation-hue transformation (ISH), TM band ratios, and edge enhancement were applied to discriminate the lithologies and structure as well as associated areas of hydrothermal alteration. Colour composites of PC1, 2 and 3, always encoded red, green and blue respectively, PC4, 3 and 2, ISH transformation of TIW: bands 1, 3 and 5, were found most suitable for lithology and boundary discrimination in the area. A colour composite of 3/1, 4/3, and 5/7 ratio images was prepared to separate altered areas. Altered areas, which have potential for mineralization, were mapped on the constructed geological map. A number of previously unmapped faults and subunits of the formations were discriminated successfully. A lineament map and rose diagram were prepared using high-pass Laplacian filters. The rose diagram showed a good correspondence with the strike of previously mapped earthquake fault breaks. The linear features of the area have dominant directions at N 30-40 degrees E and N 60-80 degrees E. Alteration and mineralization in the Korucu-Dugla area are mostly controlled by NNE and EW trending structures.