This paper argues for the existence of a discontinuous root morpheme in the Semitic languages. Although this notion is often used in the analysis of these languages, it has been claimed in some surface-oriented studies to be a mere theoretical artifact. The first part of this paper presents two arguments from the realm of verbal inflection. It is shown that no surface form can serve consistently as the base for other forms in either Modern Hebrew or Chaha, two Semitic languages. It is further argued that some morphophonological processes in Chaha must be regarded as applying to the root. Applying such processes to the surface stem would result in incorrect forms. The second part of the paper treats discontinuous effects in nominal formations. It is argued that agentive nouns in Modern Hebrew can be built either on another noun or on the root. Without the notion of the root, one is obliged to list all the cases which we propose are root-derived. Such listing obscures the entirely regular and consistently predictable form of root-derived agentives.