In the scheelit processing plant situated in Mittersill/Salzburg, scheelit is concentrated by gravity separation and severals steps of flotation. In the flotation oleic acids are used as collectors, but due to their nonselective mode of action other sparingly soluble minerals, besides scheelit, are concentrated in the flotation circuit. These minerals are predominantly calcite, apatite and fluorite. By systematic test work in a three liter lab scale flotation cell several reagents - starch, quebracho, potassium silicate, citric acid, aluminium sulphate and aluminum chloride - were evaluated for their potential of depressing apatite, fluorite and calcite. Apart from the depressing effect the scheelite recovery served as the constraint for the selection. Chemical assays of the flotation products at varied dosage of the depressants served to evaluate their effectivity. Bevorhand, the dependency of the recovery on the pH-value of scheelit, calcit apatite and fluorite, was determined and the optimal pH-value for the scheelit recovery was ascertained. As the grain size and degree of liberation are crucial for the flotation outcome, mineralogical analysis and characterisations of the ore complete the matter of the thesis.