This paper presents some results of numerical calculations of explosive boiling up of a water drop irradiated by an intense CO2—laser radiation. The theoretical model of the drop explosion has been constructed based on simultaneous solution to the boundary—value problem on thermal diffusivity through an inhomogeneousity heated drop and of the kinetic equation of vaporization of a superheated (metastable) liquid. The basic characteristics of explosive boiling up of the drop (degree of explosive vaporization, time of explosion, its energy threshold) have been investigated. It has been established that these characteristics depend on the heating rate of the drop and its radius. The results presented in this paper are indicative of the fact that two drop heating regimes can be identified in the process of explosive boiling up of large drops from the point of view of its evolution, namely, slow and fast heating regimes. This division indicates the competition among real physical processes in the irradiated drop and makes it possible to identify the salient features of explosion process.