The paper introduces PACE — a parser comparison and evaluation system for the syntactic processing of natural languages. The analysis is based on context free grammar with contextual extensions (constraints). The system is able to manage very large and extremely ambiguous CF grammars. It is independent of the parsing algorithm used. The tool can solve the contextual constraints on the resulting CF structure, select the best parsing trees according to their probabilities, or combine them. We discuss the advantages and disadvantages of our modular design as well as how efficiently it processes the standard evaluation grammars.