The Miao-Yao languages are spoken by tribes scattered among the mountainous regions of southwestern China (in the provinces of Hunan, Kueichow, Kuangtung, Kuanghsi, Yünna, Szuchuan), in Viet Nam (in the area of Tonkin), and in Thailand. These tribes bear various Chinese names, with either Miao or Yao as their last element. On the basis of the information that I now have, I have tentatively classified this group of dialects into two main divisions: the first preserves the syllable-finals -p, -t, (k), -m, the second has lost them. The dialects of the second division in turn form two subdivisions: one displays a highly complicated system of initials, the other a comparatively simple one. In this paper ten dialects are discussed: MKC (Hungchan Miao in Kaop'o, Kueichu, Kueichow), MKS (Yi Miao in Kechengchai, Kuangshun, Kueichow), YLP (Hei Yao in Yaolu, Lipo, Kueichow), YYT (Tahua Yao in Hsishankai, Yungts'ung, Kueichow), MTK (Hei Miao in Shihtungk'ou, Taikung, Keuichow), MCF (Hei Miao in Chengfeng, Keuichow), MJC (Hei Miao in Kaot'ungchai, Jungchiang, Kueichow), YYL (Yao in Yaoling, in the districts of Lienchow, Lienshan, and Yangshan in Kuangtung), YHN (Ch'ing-yi Yao in Haining, Tonkin, Viet Nam), YTP (Tapan Yao in Tonkin, Viet Nam). Most of these dialects belong to the second main division; MKC, MKS, and YLP differ from MTK, MCF, MJC, and YYT by having nasal-prefixed initials (stops and affricates) and initial consonant clusters with -l- or -r- as the second element. The dialects of the first main division are YYL, YHN, and YTP; they are cited only to show the distinctive finals -p, -t, (-k), -m. The many seemingly irreconcilable irregularities in the phonology of the three Yao dialects YYL, YHN, and YTP may be due to the inaccuracy of the records made by Wong and Savina.