The counterpressure structural foam process, although not new, is generating increasing interest in the structural foam community. Initial development work began as far back as the mid-1950s in Europe. The driving impetus for its development has been the surface enhancement that it provides. While this improvement is important and beneficial, it is not the only benefit of the process. The purpose of this paper is to discuss the effect of the counterpressure process on the mechanical properties and behavior of counterpressure-processed engineering structural foam.