This focused issue of Computers and Operations Research contains seven

excellent papers on the application of optimization and metaheuristic search techniques to problems in software engineering. The focused issue arises from a call for papers, for which a total of 18 papers were received. After careful and detailed refereeing, a total of 7 papers were finally selected for inclusion in the focussed issue. Optimization and search based techniques have been applied to a wide range of software engineering problems, using a large number of techniques associated with OR. This area of research has come to be known as Search Based Software Engineering (SBSE) [5, 10]. The past five years have witness a dramatic growth in conferences, workshop, tracks, and special issues on SBSE. Previous work on SBSE spans the spectrum of software engineering problems from requirements engineering [2], project planning and cost estimation [1, 8, 12], through test data generation [13], to automated maintenance [3, 9, 14, 15, 16], service-oriented software engineering [4], compiler optimization [6, 7] and quality assessment [11]