In a recent paper, Clahsen and Muysken (1986) argue that adult second lan guage (L2) learners no longer have access to Universal Grammar (UG) and acquire the L2 by means of learning strategies and ad hoc rules. They use evidence from adult L2 acquisition of German word order to argue that the rules that adults use are not natural language rules. In this paper, we argue that this is not the case. We explain properties of Germanic word order in terms of three parameters (to do with head position, proper government and adjunc tion). We reanalyse Clahsen and Muysken's data in terms of these parameters and show that the stages that adult learners go through, the errors that they make and the rules that they adopt are perfectly consistent with a UG incor porating such parameters. We suggest that errors are the result of some of the parameters being set inappropriately for German. The settings chosen are nevertheless those of existing natural languages. We also discuss additional data, from our own research on the acquisition of German and Afrikaans, which support our analysis of adult L2 acquisition of Germanic languages.