The　primary　goal　is　the　kinematic　and　dynamic　analysis　of　a　spatial　3　degree-of-freedom　parallel　manipulator　(a　3-RRS　parallel　manipulator).　The　architecture　of　the　mechanism　is　comprised　of　a　moving　platform　attached　to　a　fixed　platform　through　three　identical　revolute-revolute-spherical　jointed　serial　linkages.　A　complete　description　of　the　position　and　orientation　of　the　moving　platform　with　respect　to　the　reference　frame　requires　six　variables,　i.e.,　the　three　Cartesian　coordinates　of　a　reference　point　on　the　moving　platform　and　three　angles.　However,　since　the　parallel　manipulator　has　two　degrees　of　orientation　freedom　and　one　degree　of　translatory　freedom,　which　implies　that　only　three　variables　can　be　specified　independently.　Firstly,　the　constraint　equations　describing　the　inter-relationship　between　the　six　motion　coordinates　of　the　moving　platform　are　derived.　Closed　form　solutions　to　the　constraint　equations　are　found　which　provide　the　constrained　variables　as　functions　of　the　unconstrained　(specified)　variables.　Some　significant　conclusions　are　drawn　from　the　closed　form　solutions.　Then,　the　dynamic　equations　of　the　parallel　manipulator　are　presented　on　the　basis　of　Lagrange　equation.　Based　on　the　dynamic　model,　the　angular　velocities,　the　driving　force　or　torque　and　consumed　energy　of　the　actuators　are　analyzed　through　an　example.　The　analysis　provides　necessary　information　for　dynamic　performance　analysis,　optimal　design　and　control　of　the　parallel　mechanism.　©2009　Journal　of　Mechanical　Engineering.