Today, there exist a number of process repositories with the aim of supporting the reuse of process models. Designing such repositories is a complex task, which should be guided by clear requirements. In order to support the development of future process repositories, we propose and justify a set of requirements for such repositories. These requirements are based on a number of essential properties of process repositories as well as a set of use cases. Furthermore, we carry out a survey and evaluation of a number of existing repositories based on the requirements identified in this paper.