Conventional　stability　analysis　of　rock　slopes　during　earthquakes　is　often　confined　to　vertically　propagated　ground　motions.　One　of　the　main　reasons　for　the　limitation　is　due　to　the　lack　of　a　rational　yet　simple　way　to　apply　an　input　motion　of　a　specific　incident　angle.　In　this　study　a　method　of　ground　motion　input　was　implemented　fur　this　application　in　analyzing　a　jointed　rock　slope.　In　a　nutshell,　it　involved　extending　a　problem　domain　by　wrapping　it　with　an　elastic　region　and　converting　the　incident　waves　into　nodal　forces　in　addition　to　make　a　boundary　non-reflecting.　The　approach　is　general,　but　here　only　the　plane　strain　problem　was　tackled　and　thus　only　two　dimensional　P-wave　was　considered.　A　jointed　rock　is　defined　by　an　elastic　modulus,　a　Poisson　ratio,　the　joint　orientations　and　the　strength　of　the　joints.　A　1:1　jointed　rock　slope　of　30　m　in　height　was　used　as　the　base　rock　slope.　An　El　Centro　record　of　1979　was　employed　as　the　base　ground　motion.　Three　incident　angles　were　considered　in　the　analysis.　Results　obtained　indicated　that　incident　angles　do　have　a　significant　impact　on　the　stability　of　a　jointed　rock　slope,　and　the　severity　of　the　impact　depended　on　the　relative　orientation　of　the　incident　wave　with　respect　to　that　of　the　joints.　Copyright　©　2014　ARMA.