The paper investigates a complex word order phenomenon in German and the interaction of syntax and information structure it exemplifies: the occurrence of subjects as part of a fronted non-finite constituent and particularly the so-called definiteness effect excluding (many) definite subjects from this position. We explore the connection between focus projection and the partial fronting cases and show that it is the subject of those verbs which allow their subject to be the focus exponent that can be included as part of a fronted verbal constituent. In combination with the observation by Webelhuth (1990) that fronted verbal constituents need to be focused, this provides a natural explanation of the definiteness effect in terms of the information structure requirements in these sentences. Interestingly, the generally ignored exceptions to the definiteness effect are predicted by our analysis; we show that they involve definite noun phrases which can bear focus, which allows them to be part of a fronted verbal constituent. Finally, building on the integrated grammatical architecture provided in De Kuthy (2002), we formulate an HPSG theory which captures the interaction of constraints from syntax, information structure and intonation.