Abstract. Answer Set Programming is a new paradigm based on logic programming. The main component of answer set programming is a system that finds the answer sets of logic programs. Generally, systems utilize some heuristics to choose new literals at the choice points. The heuristic used in this process is one of the key factors for the performance of the system. A new heuristic for answer set programming has been developed. This heuristic is inspired by hierarchical planning. The notion of criticality, which was intror generating abstraction hierarchies in hierarchical planning, is used in this heuristic. The resulting system (CSMODELS) uses this new heuristic and is based on the system SMODELS. The experimental results show that this new heuristic is promising for answer set programming. CSMODELS generally takes less time than SMODELS to find an answer set.