In 1956 Don Patinkin described Léon Walras' theory of tâtonnement as “one of his most imaginative and valuable contributions to economic analysis,” and rightly lamented its neglect and disparagement up to that date (Patinkin, 1956, p. 377). Since the appearance of Patinkin's authoritative exposition of the theory in the first edition of his Money, Interest and Prices, there has been a profusion of ingenious articles on tâtonnement so that the repetition of this lament in 1965, in the second edition of his treatise (Patinkin, 1965, p. 531), now appears an anachronism. On the other hand, when Patinkin repeats his complaint that Walras' theory of tâtonnement has been misunderstood, he is surely justified. The current reformulations of the theory, though they proudly bear the Walras patronymic, display only a distant family resemblance to their ancestral prototype, for the infusion of new technical refinements has all but obliterated any recognizable similarity between the descendant theories and their progenitor. Moreover, the latter-day emendations and the niceties of modern analysis have so colored the recent exegetical comments on Léon Walras' own theory that the criticism has often been misdirected, finding fault with Walras' handling of subtle issues which, for want of hindsight and the techniques of a late twentieth-century economist, he had not even raised. This is my excuse for retracing and reappraising once more Léon Walras' theory of tâtonnement as it was first developed in the Éléments d'Économie Politique Pure.