This book is an overview of the most relevant collision resolution algorithms used in contention-based multiple access protocols to handle collisions among users contending for channel access. The two main categories of collision resolution algorithms are the so called backoff and the splitting algorithms. The described backoff algorithms are further classified into p-persistent, binary exponential, X-Increase Y-Decrease and dynamic optimum backoff window algorithms. On the other hand, the splitting algorithms are basically characterized as gated-access, window-access and free-access. The dynamic tree algorithm and some limited sensing algorithms are also discussed. Other proposals that cannot be classified in the previous categories are also presented. Finally, examples of MAC protocols for wireless communications that make use of some of the aforementioned collision resolution algorithms are included.