Core vocabularies of five major dialects of Rejang are derived from Proto- Malayo-Polynesian etyma mediated by a reconstructed protolanguage, Proto- Rejang, crucial evidence for which is provided by Rawas, a previously neglected dialect. Every etymon turns out to be reconstructable on the basis of just two dialects-either Rawas and Pesisir or (more often) Rawas and Kebanagung. One clear conclusion is that the Rawas area represents the oldest Rejang settlement in Sumatra. While a few minor claims made in previous work on Rejang historical phonology are corrected or refuted by the Rawas evidence, the most important findings are confirmed. Thus, (a) individual Rejang dialects have undergone more changes (splits and mergers) of Proto-Malayo-Polynesian vowels than any other known Austronesian group; (b) Proto-Rejang underwent two accent shifts, first to a Malay-type pattern (a modified form of penultimate word-stress) and then to the contemporary word-final stress pattern; and (c) complex conditions, including vowel harmony conditions, are needed to preserve regularity in the majority of sound changes affecting Rejang dialects.