  We present a simple approach for automatically extracting the number of
subjects involved in randomised controlled trials (RCT). Our approach first
applies a set of rule-based techniques to extract candidate study sizes from
the abstracts of the articles. Supervised classification is then performed over
the candidates with support vector machines, using a small set of lexical,
structural, and contextual features. With only a small annotated training set
of 201 RCTs, we obtained an accuracy of 88\%. We believe that this system will
aid complex medical text processing tasks such as summarisation and question
answering.
