The subject of this extensive corpus-based study is the distribution and the functional role played by a total of 22 indefinite nouns in 9 key texts for Italian linguistic and literary history dating from the late 13th to the early 16th century (including »Novellino«, »Decameron«, and Bembo's »Prose«). The central issue is the semantic and functional differentiation of these indefinite forms as encountered in the texts. This is pinpointed by way of comparison with their Latin etyma and modern Italian equivalents. A further essential aspect is the problem of the grammaticalization of indefinite noun determinants in Italian and the Romance languages in general.