Gravity investigations in mountainous areas have been traditionally performed along profiles located in the valleys due to the extremely rugged topography. Errors up to 10 mGal can be caused due to fault structures or low density sediments filling the valleys. Gravity stations have therefore to be distributed in a grid system with many stations high up mountain flanks and tops. This station pattern necessitates remarkable changes in measuring techniques and reduction procedures for a gravity survey. In this case the site coordinates are a source for considerable gravity errors besides the station heights, as the accuracy of topographic corrections also depends on the error of station coordinate determination. Topographic corrections have to be performed by high resolution techniques and the radius of the correction area must be extended to 167 km. The gravity effect of lakes and glaciers has also to be considered. The problems are discussed using case histories from the Eastern Alps. The improvements gained by expanded reduction procedures are demonstrated.