In recognition of its crucial role in spray combustion, the characteristic property of interactive droplet vaporization and combustion is reviewed in the light of a generalized asymptotic theory which is presently developed in order to gain deeper insight into the underlying physics of spray combustion at near-atmospheric pressures. Emphasis is placed on geometrical significance in excitation of group vaporization/combustion modes. It is shown that a criterion for the onset of group combustion is expressible in the form of a local relationship between the ratio of droplet separation distance to droplet radius, (l) over bar = ((a) over bar(0)(3) (n) over bar)(-1/3), the unsteadiness parameter for single droplet combustion, epsilon = [2(<(rho)over bar>(infinity)/<(rho)over bar>*)1n(1 + B)](1/2). An attempt is also made to clarify the validity of the existing continuum theory from microscopic droplet interaction considerations.