We present a tool developed for annotating corpora with argument structure representations. The presentation focuses on the architecture of the annotation scheme and a number of techniques for increasing the efficiency and accuracy of annotation. Among others, we show how the assignment of grammatical functions can be automatised using standard part-of-speech tagging methods. 1 The Annotation Scheme Several features of the tool have been introduced to suite the requirements imposed by the architecture of the annotation scheme (cf. (Skut et al., 1997)), which can itself be characterised as follows: • Direct representation of the underlying argument structure in terms of unordered trees; • Rudimentary, flat representations; uniform treatment of local and non-local dependencies; • Extensive encoding of linguistic information in grammatical function labels. Thus the format of the annotations is somewhat different from treebanks relying on a context-free backbone augmented with trace...