This chapter discusses how to make computationally intensive tasks more efficient by distributing the calculations among several cores in a single computer or even among several computers in a grid. All of this can be done using Wolfram Research products such as: grid Mathematica and Wolfram Lightweight Grid Manager. The chapter describes complementary tools such as Workbench, an excellent Integrated Development Environment for large Mathematica-based projects, and web Mathematica, perfectly suited to develop programs that run in a web server and can be executed from any browser. It provides some new functionality added to newest Mathematica version, wavelet analysis, and control systems. Parallel computing consists of breaking down programs into discrete components which can be executed simultaneously. In Mathematica, this is done by distributing the individual program parts among multiple kernels. The function Parallel Evaluate evaluates an expression in different kernels and returns the result from each one of them. This function is commonly employed in calculations involving Monte Carlo simulation.