Each of all the existing theories of the acoustic radiation pressure has, of course, peculiar excellent advantages.It is also the fact, however, that there are more or less ambiguities, leaps in logic, and unnecessary assumptions in many existing theories.The purpose of the present paper is to develop a general theory that covers both the Rayleigh and Langevin radiation pressures, and is simple and easy to understand, with merits of existing theories incorporated as far as possible.We distinguish between the Rayleigh and Langevin radiation pressures according as the force acting on an obstacle depends on a fractional change in static pressure or not.Since it is a matter of the experimental conditions whether one observes the Rayleigh radiation force or the Langevin radiation force, both radiation forces should be treated theoretically from a common physical point of view.The emphasis is placed on pointing out that the tensor properties cannot be disregarded in the Rayleigh radiation pressure as well as in the Langevin radiation pressure, by showing where the tensor term originates in.A brief review is given for a few of existing theories at the end of the chapter.