This volume contains the proceedings of the 13th Colloquium on Trees in Algebra and Programming (CAAP '88), held in Nancy, March 21-24, 1988. The preceding 12 colloquia were held in France, Italy and Germany. CAAP '85 and CAAP '87 were integrated into the International Joint Conference on Theory and Practice of Software Development, TAPSOFT (see Lecture Notes in Computer Science volumes 185 and 249). As another effort to link theory and practice in computer science, CAAP '88 was held in conjunction with the European Symposium on Programming, ESOP '88 (see volume 300 of this Lecture Notes series). CAAP '88 is a conference in the area of program development and programming concepts but, following the tradition, is devoted to theoretical aspects, and especially to Trees, a basic structure of computer science. A wider range of topics in theoretical computer science is also covered. The papers are on word, tree or graph languages, with algorithmic or complexity studies, on abstract data types (another classical topic of CAAP) and/or term rewriting systems and on non-standard logics, and parallelism and concurrency.