In the last decades, the idea that the definite adjectives in Balto-Slavic arose from constructions with a relative pronoun has become firmly established in the field of Indo-European linguistics as the mainstream view on the subject. The competing analysis, which holds that these forms go back to constructions involving a demonstrative, has by and large been discarded. In the present article, I will investigate the presuppositions of this view and the available evidence anew. It will become clear that the definite adjectives are best derived from nominal constructions with a definiteness marker. Such a development is in accordance with general crosslinguistic trends and can additionally be backed up by findings from areal linguistics. The arguments adduced in favor of the relative hypothesis, on the other hand, can be shown to lend themselves easily to an integration into a scenario involving an original definiteness marker.