A half of inflectional forms of /naga-da/ class and/nas$^$h/∂-da/ class verbs in Yeongnam and Yeongdong dialects have peculiar pitch patterns which can not be derived by normal pitch realization rules. These peculiar pitch patterns are in correspondence systematically among modern southeastern dialects. But correspondence relation does not appear between Midieval Korean and modern southeastern dialects. In order to explain the above two phenomena we cannot but hypothesize the existence of Proto-Yeongnam-Yeongdong Dialect before the 15th century.