A large number of proposals have been put forward concerning the structure of Proto-Basque roots and syllables. However, previous research is lacking in specific heuristics used to establish these structures. In the first part of this chapter, I offer a set of heuristics for identifying roots in Proto-Basque. These include the syntagmatic strategies of past researchers, as well as new paradigmatic features, including three Proto-Basque prefixes (nominalizer, verbalizer and collective nominalizer) and a nominalizing suffix *-s. With these heuristics in hand, mono- and di-syllabic roots of different shapes are discovered, contesting the constrained CVC root-theory of Lakarra. Proto-Basque syllable structure must be revised to take into account evidence for initial *sT clusters, where T is *ph, *th, or *kh. The proposed syllable template is *(s)(C)V(R)(s), where C is any consonant except *r, and R is *r, *l, or *n. The disyllabic *h-medial stems introduced in Chapter 2 are revisited, as their shape changes from disyllabic to monosyllabic when affixed.