This volume contains the proceedings of MPC 2000, the fifth international coference on Mathematics of Program Construction. This series of conferences aims to promote the development of mathematical principles and techniques that are demonstrably useful and usable in the process of constructing c- puter programs (whether implemented in hardware or software). The focus is on techniques that combine precision with concision, enabling programs to be constructed by formal calculation. Within this theme, the scope of the series is very diverse, including programming methodology, program specification and transformation, programming paradigms, programming calculi, and progr- ming language semantics. The quality of the papers submitted to the conference was in general very high. However,the number of submissions has decreased compared to the pre- ous conferences in the series. Each paper was refereed by at least five and often more committee members. In order to maintain the high standards of the coference the committee took a stringent view on quality; this has meant that, in some cases, a paper was rejected even though there was a basis for a good coference or journal paper but the submitted paper did not meet the committee’s required standards. In a few cases a good paper was rejected on the grounds that it did not—t within the scope of the conference.