International audience ; The method of internal reconstruction is used to analyze the structure of verbal roots in two Tibeto-Burman languages of the Kiranti group in Nepal.Part I presents an internal reconstruction of the verbal roots and stems of Bahing, based on an extensive presentation of the complex morphological agreement paradigm. Part 2 presents a reconstruction of the verbal roots of Khaling, based on the two forms presented for each verb in a published dictionary. The two-tone system observed is shown to reflect the opposition between roots reconstructed with (unvoiced) stop finals (high tone) and vocalic or sonorant finals (low tone). Although each languages has 10 phonological vowels, a five-vowel system is shown to be adequate to characterize the reconstructed roots in both cases, once vowel harmony and the influence of syllable finals on syllable vowels are taken into account.