The study of complementarity problems is now an interestingmathematical subject with many applications in optimization,game theory, stochastic optimal control, engineering,economics etc.This subject has deep relations with important domains offundamental mathematics such as fixed point theory, orderedspaces, nonlinear analysis, topological degree, the study ofvariational inequalities and also with mathematical modelingand numerical analysis.Researchers and graduate students interested in mathematicalmodeling or nonlinear analysis will find here interestingand fascinating results.