The QAPLIB is a collection of data instances for the Quadratic Assignment Problem (QAP), providing detailed information on each instance, including whether the problem is solved to optimality and the best known bounds if not. It also surveys available software and recent dissertations related to QAP. The QAPLIB was first published in 1991 as a unified testbed for QAP, and was updated in 1994 with new instances and current best solutions. The current version is available via the World Wide Web and is regularly updated. It includes the largest instance of size n = 256. Problem instances are listed alphabetically by authors or contributors and are pure quadratic, with symmetric examples unless stated otherwise. The data format for instances with filename extension “dat” includes n, followed by matrices A and B, representing flow or distance matrices. The QAP is formulated as minimizing the sum over i and j of a_ij * b_{p(i),p(j)}, where p is a permutation. The QAPLIB provides contact addresses for Stefan E. Karisch and Franz Rendl, and includes URLs for the QAPLIB Home Page. The library reflects changes in electronic communication and increased research activities around QAP, including a list of recent dissertations.The QAPLIB is a collection of data instances for the Quadratic Assignment Problem (QAP), providing detailed information on each instance, including whether the problem is solved to optimality and the best known bounds if not. It also surveys available software and recent dissertations related to QAP. The QAPLIB was first published in 1991 as a unified testbed for QAP, and was updated in 1994 with new instances and current best solutions. The current version is available via the World Wide Web and is regularly updated. It includes the largest instance of size n = 256. Problem instances are listed alphabetically by authors or contributors and are pure quadratic, with symmetric examples unless stated otherwise. The data format for instances with filename extension “dat” includes n, followed by matrices A and B, representing flow or distance matrices. The QAP is formulated as minimizing the sum over i and j of a_ij * b_{p(i),p(j)}, where p is a permutation. The QAPLIB provides contact addresses for Stefan E. Karisch and Franz Rendl, and includes URLs for the QAPLIB Home Page. The library reflects changes in electronic communication and increased research activities around QAP, including a list of recent dissertations.