The applicability of the laser flow tagging technique is investigated for velocity measurements in the liquid phase of diesel sprays. This is done under atmospheric and near-engine-like boundary conditions in a constant volume chamber. Measurements are conducted in the primary, breakup zone of the spray, where other optical techniques like particle image velocimetry or phase Doppler anemometry cannot be applied. A phosphorescent tracer dissolved in the model fuel is excited by a short UV laser pulse. By means of an appropriate optical setup, phosphorescent tag lines are generated in the spray. Using an image-intensified charge-coupled device (CCD) camera, the displacement, and therefore the velocity of the tagged droplets is determined.