he static balancing of spatial three-degree-of-freedom (3-dof) parallel mechanisms or manipulators with revolute actuators using counterweights or springs is studied in this paper. The expressions for the position vector of the center of mass and the total potential energy of the mechanism are first obtained. Then, the kinematic constraint equations of the mechanism are introduced in order to eliminate some of the dependent variables from the expressions. Finally, the conditions for the static balancing of the mechanism are derived from the resulting expressions. Two examples corresponding to the two balancing methodologies are given in order to illustrate the results.