Parallel programming is being seen as the only cost-effective method to improve performance of computer applications. A well-structured parallel application can achieve better performance in terms of execution speed over the sequential execution on existing and upcoming parallel computer architecture. This book named Power of Parallelism in.NET, describes the experimental evaluation of different parallel application performance with thread-safe data structure and parallel constructions in.NET framework. It describes different performance issues of parallel application development. Before describing the experimental evaluation, this book describes some methodologies relevant to parallel programming, such as Parallel Computer Architecture, Memory Architectures, Parallel Programming Models, Decomposition, Threading etc. It describes the different APIs in.NET framework and the way of coding for making an efficient parallel application depends on problem definition. Moreover, this book describes Improper Partitioning, Over-subscription, Improper Workloads and more. The parallel application models and the evolving example of parallel programming is well-illustrated in this book.