Very few of the languages of the Tai family still preserve consonant clusters of the type pl-, kl-, pr-, kr- , etc. The two languages generally known to preserve such clusters, at least in part, are Siamese and Ahom, the latter an extinct language of Assam. The dialects of Wu-ming and Lung-an, both in central Kwangsi province, are the other dialects I know which preserve them to a certain extent. The widely scattered distribution of these languages shows that the preservation of the clusters indicates no specially close linguistic relationship among them. Three other languages—Lao, a language closely related to Siamese; Shan, closely related to Ahom; and Dioi of Kweichow province, with which Wu-ming shares many common characteristics—have all simplified such clusters. It is safe to assume that the simplification is in most cases an individual dialect development, and that the clusters persisted in each of the various dialect groups before their simplification took place.