This paper is concerned with the serialization of argument clauses (AC) and relative clauses (RC) in the German Nachfeld. We discuss examples provided by Haider (1994) who claims that only RC>AC is grammatical. Our claim is that in most contexts, the serialization is optional; but in some contexts, there is a gradient preference for RC>AC. There are no constraints which rule out AC>RC categorically. An experiment obtaining grammaticality judgments on sentences with permuted syntactic functions of these clauses confirms that none of the two serializations is ruled out. The preference for RC>AC arises if in the base, one of the Cps c-commands the other. We propose an approach based on Stochastic Optimality Theory in order to analyze the data under discussion.