Expressions for the electrostatic force and torque on an isolated body immersed in a dielectric medium have been developed for the case where the imposed electric field is either uniform or varies linearly with position. The expressions apply to a body of general shape that carries no net native charge; illustrative examples are provided for ellipsoidal and spheroidal bodies. The force on a body in a uniform field is shown to be zero, which rectifies an incorrect result derived previously by others. The expressions obtained can be adapted to dielectric, leaky dielectric and perfectly conducting bodies subject to either de or ac forcing fields.