In this paper I focus on the history of Lithuanian and Latvian round numerals. There is evidence to suggest that the original IE. forms may have been the outcome of a prehistorical semantic shift from substantives to numerals. Baltic languages support this view displaying archaic noun-like features in both morphology and syntax. A diachronical review from the first written documents reveals that other changes have occurred involving morpho-phonology, syntax and semantics. According to chronological data, I suggest a possible interpretation of the historical interplay among the above-mentioned phenomena. Then some Baltic peculiarities in the IE. context are pointed out, as well as the main historical divergences between Lithuanian and Latvian.KEY WORDS: Indo-European (Baltic) numerals, round numerals, partitive model, semantic shift, morpho-phonological reduction
