  In this paper, we discuss the leading order correction to the equation of
motion of the particle, which presumably describes the effect of gravitational
radiation reaction. We derive the equation of motion in two different ways. The
first one is an extension of the well-known formalism by DeWitt and Brehme
developed for deriving the equation of motion of an electrically charged
particle. In contrast to the electromagnetic case, in which there are two
different charges, i.e., the electric charge and the mass, the gravitational
counterpart has only one charge. This fact prevents us from using the same
renormalization scheme that was used in the electromagnetic case. To make clear
the subtlety in the first approach, we then consider the asymptotic matching of
two different schemes, i.e., the internal scheme in which the small particle is
represented by a spherically symmetric black hole with tidal perturbations and
the external scheme in which the metric is given by small perturbations on the
given background geometry. The equation of motion is obtained from the
consistency condition of the matching. We find that in both ways the same
equation of motion is obtained. The resulting equation of motion is analogous
to that derived in the electromagnetic case. We discuss implications of this
equation of motion.
