Abstract: The present invention relates to a viscous material pump. According to the invention, a pressure sensor is associated with the hydraulic drive cylinder of the fixed displacement pump for generating a pressure signal when a first sudden pressure increase occurs after the drive piston moves out of its end position. The volume subsequently displaced by the conveying piston corresponds to the actual delivery volume during the pumping stroke. A processor calculates the actual delivery volume for each pumping stroke using the ratio between the stroke time, as defined by the occurrence of the pressure peak and the maximum available conveying volume of the cylinder, as defined by the stroke time the piston needs to move from its first to its second end position. The present invention further provides for adjusting the supply volume of a supply means discharging the material to the viscous material pump.