The primary object of the lecture notes is to develop a treatment of association schemes analogous to that which has been so successful in the theory of finite groups. The main chapters are decomposition theory, representation theory, and the theory of generators. Tits buildings come into play when the theory of generators is developed. Here, the buildings play the role which, in group theory, is played by the Coxeter groups. - The text is intended for students as well as for researchers in algebra, in particular in algebraic combinatorics.

The present text is an introduction to the theory of association schemes. We start with the de?nition of an association scheme (or a scheme as we shall say brie?y), and in order to do so we ?x a set and call it X. We write 1 to denote the set of all pairs (x, x) with x? X. For each subset X ? r of the cartesian product XX, we de?ne r to be the set of all pairs (y, z) with (z, y)? r.For x an element of X and r a subset of X X, we shall denote by xr the set of all elements y in X with (x, y)? r. Let us ?x a partition S of XX with / S and 1 ? S, and let us assume X ? that s ? S for each element...