It is shown that Leon Walras developed two separate theories of tatonnement. One is a disequilibrium-production model. The other is a pledges model, in which transactions and production occur only at the equilibrium set of prices. These models are explained, and the manner in which they appear in the vari ous editions of Walras's Elements is used to account for the developm ent of conflicting interpretations of his writings on tatonnement. It is shown that the disequilibrium-production model is more representa tive of Walras's work than the pledges model and that the latter is i ncompatible with the theories of particular aspects of economic behav ior on which the Elements depends for its verisimilitude and explanat ory power. Copyright 1987 by University of Chicago Press.