The present article examines asyndetic or conjunctionless conditionals in German and English. According to Jespersen’s Model (1940), this construction arose diachronically from a paratactic discourse sequence with a polar interrogative, but more recently Harris and Campbell (1995) have claimed that this model lacks any theoretical and empirical foundation. To demonstrate how asyndetic conditionals may emerge from discourse, this study reframes Jespersen’s Model in grammaticalization terms and adduces several constructional features in order to show that a grammaticalization process has actually taken place. In particular, this is achieved by applying traditional grammaticalization parameters such as bondedness, paradigmatic variability and specialization to synchronic and diachronic variation patterns with regard to clause integration, the finite verb of the protasis and the possible-world categories realis, potentialis, irrealis. The article also explores the relevance of speech-situation evocation to the formation of interrogative-based conditionals
