Four innovations in the Proto-Basque consonant system are argued for in this chapter, each with a wide range of implications for reconstruction and external comparison. First, evidence is presented that Proto-Basque had a proto-phoneme *m. Second, evidence is presented that Proto-Basque had a proto-phoneme *ph. Third, it is shown that the full series of voiceless stops is best analyzed as voiceless aspirated *ph, *th, *kh. Arguments for an aspirated series include distribution of aspiration in *h-ful dialects, the sound change of initial debuccalization, for which a great deal of new evidence is put forward, and a range of constraints on the distribution of *h and voiceless stops in earlier stages of the language. All previous reconstructions of Proto-Basque assume a contrast between two sibilants: *s an apical and *z a laminal. The final proposal in this chapter is that there was only a single sibilant *s in Proto-Basque. All inherited instances of *z are derived from *s in *sC and *Cs consonant clusters.