An atomization and drop breakup model for high-pressure-driven liquid fuel sprays is presented, tuned, and validated. The breakup criterion is determined by the Taylor drop oscillator, and each breakup event reflects the experimentally observed drop disintegration mechanism of either bag, stripping, or catastrophic breakup. The formation of a fragmented liquid core resulting from inner-nozzle disturbances is achieved by subjecting the initial drops to a primary breakup process followed by a cascade of drop breakups. The primary breakup is simulated by providing the injected drops with appropriate initial deformation velocities such that experimentally, observed breakup lengths are obtained The model has been tuned and validated by means of experimental data for nonevaporating, evaporating, and reacting sprays under controlled conditions in constant-volume or constant-pressure vessels. In addition, simulated temporal and spatial fuel volume fraction distributions in the near-nozzle region have been found to be in good agreement with X-ray measurements. These support the existence of a fragmented liquid core at the nozzle exit and confirm that the region of maximum liquid density occurs at the leading edge of the spray.