The work Πϵρὶ ἁπλῶν φαρμάκων or De simplicibus (Simp., also known as Πϵρὶ ϵὐποριστῶν) is ascribed in the MSS to Dioscorides. This ascription, first found in Oribasius (fourth century AD), was accepted by the most recent editor of the work, Max Wellmann, and is enshrined in LSJ, but has often been questioned. This article aims to disprove Dioscoridean authorship on the grounds of two characteristics of Simp.: first, its use of alphabetical organization; second, its unsatisfactory treatment of material that is better handled in Dioscorides’ De materia medica (MM). The use of alphabetical ordering in Simp. is inconsistent and frequently disrupted; furthermore, in the preface to MM, Dioscorides explicitly rejected alphabetization as a means of organizing lists of medications. Internal evidence shows that the author of Simp. made ineffectual attempts to conceal the alphabetical ordering of his material, possibly in response to Dioscorides’ criticism of that method. In its treatment of material that is paralleled in MM, Simp. sometimes lacks clarity or omits important details or makes errors, failings that would be highly unlikely if Dioscorides himself were its author.