The 4th Annual International Conference on Combinatorial Optimization and Applications (COCOA 2010) took place in Big Island, Hawaii, USA, December 18 20, 2010. Past COCOA conferences were held in Xi an, China (2007), Newfoundland, Canada (2008)and Huangshan, China (2009). COCOA2010providedaforumforresearchersworkingintheareasofcom- natorial optimization and its applications. In addition to theoretical results, the conference also included recent works on experimental and applied research of general algorithmic interest. The Program Committee received 108 submissions from more than 23...