Stability analysis of discontinuous rock masses has long been a field of interest for rock engineers. Among few methods, which have been introduced so far, the recent geometrical method called block theory, has found to be suitable, especially for the stability analysis of tunnels and underground spaces. In this study, block theory has been used for the stability analysis of abutments of Karoon IV Dam in southern Iran. In this respect, first the key blocks have been defined, using the mapped discontinuities. Then the resultant stresses, excreted by the dam, water, block weights and earthquake, have been calculated, using stereographic projection and limiting equilibrium methods. Hiring these data in block theory, the failure modes and the magnitude of forces required for failure, have been defined as a function of discontinuities' friction. Finally, safety factors have been estimated for each block. Present study showed that, all the selected blocks in the abutments of Karoon IV are safe, with regard to the supposed assumptions. Checking the mentioned results with the limiting equilibrium method of Hoek and Bray showed that the block theory gives a lower value of safety factor, almost universally. As the sensitivity of block theory to the changes in the factors responsible for the instability of blocks is higher, and as it can be used for the blocks with any number of faces, the block theory could be applied instead of limiting equilibrium methods, in the stability analysis of dam abutments and open pit mines.