This volume contains papers presented at the secondInternational Workshop on Word Equations and Related Topics(IWWERT '91), held at the University ofRouen in October1991.The papers are on the following topics: general solution ofword equations, conjugacy in free inverse monoids, generalA- and AX-unification via optimized combination procedures,wordequations with two variables, a conjecture aboutconjugacy in free groups, acase of termination forassociative unification, theorem proving by combinatorialoptimization, solving string equations with constantrestriction, LOP (toward a new implementation of Makanin'salgorithm), word unification and transformation ofgeneralizedequations, unification in the combination ofdisjoint theories, on the subsets of rank two in a freemonoid (a fast decision algorithm), and a solution of thecomplement problem in associative-commutative theories.