CVC4 is an efficient open-source automatic theorem prover for satisfiability modulo theories (SMT) problems. It can be used to prove the validity (or, dually, the satisfiability) of first-order formulas in a large number of built-in logical theories and their combination. CVC4 is the fourth in the Cooperating Validity Checker family of tools (CVC, CVC Lite, CVC3) but does not directly incorporate code from any previous version. A joint project of NYU and U Iowa, CVC4 aims to support the features of CVC3 and SMT-LIBv2 while optimizing the design of the core system architecture and decision procedures to take advantage of recent engineering and algorithmic advances. CVC4 is intended to be an open and extensible SMT engine, and it can be used as a stand-alone tool or as a library, with essentially no limit on its use for research or commercial purposes.