A word list of 3,343 items with Standard Thai, English and Vietnamese glosses was used for eliciting the Black Tai or Tai Dam language data at each of the twelve research sites: ten in northern Vietnam, one in northern Laos, and one in central Thailand. The data collected at two villages in Muong Vat could not be used for a reconstruction of Old Black Tai phonological system and a lexicon because on a phonological basis and a lexical basis, the Tai dialect of Muong Vat is not Black Tai, especially the one spoken at Ban Phat, Chieng Pan sub-district and Ban Coc Lac, Tu Nang sub-district, Son La province, Vietnam.