A multidimensional model for sprays is employed to study the processes that control liquid penetration in vaporizing Diesel sprays. The computed results are compared with measured results of the penetration reported in the literature for a wide range of conditions. The computed results imply that the maximum penetration is controlled by the rate of vaporization of the liquid drops, which in turn is controlled to a large extent by the rate of entrainment of the ambient air by the spray. This is, in part, consistent with a prior explanation given by Siebers (1999) based on scaling law analysis though the analysis also found that the penetration is dependent on entrainment alone. Possible explanations for the differences are discussed. This study also points towards possible relationships between drop size and injection and ambient variables that an atomization model for Diesel sprays should have. The dependence of the conclusions on the model employed is also discussed.