This paper reports on a test of the validity of Pienemann's (1998) Processability Theory(PT). This theory predicts that certain morphological and syntactic phenomena are acquired in afixed sequence. Three phenomena were chosen for this study: attributive adjective morphology,predicative adjective morphology, and subordinate clause syntax (placement of negation). Thesephenomena are located at successive developmental stages in the hierarchy predicted by PT. Wetest whether they actually do appear in this predicted hierarchical order in the L2 of Danish,Norwegian, and Swedish learners. The three languages mentioned are very closely related andhave the same adjective morphology and subordinate clause syntax. We can, therefore, treat themas one language for the purposes of this study. Three analyses have been carried out: The firstfollows Pienemann's theory and is concerned only with syntactic levels; the second is asemantic analysis of the acquisition of number versus that of gender; the third analysis studies thevarious kinds of mismatches between the inflection of the noun, the controller, and the adjective.The results are the following: The first test supports PT as it has been described by Pienemann.The second analysis shows that there is an acquisitional hierarchy such that number is acquiredbefore gender (in adjectives), and the mismatch analysis raises questions about the fundamentalassumptions of the theory.