While the public has increasingly access to medical information, specialized medical language is often difficult for lay people to understand and there is a need to bridge the gap between specialized language and lay language. As a first step towards this end, we describe a method to build a comparable corpus of lay and specialized medical French documents and to identify similar text segments of lay and specialized language. Among the top 400 segment pairs retrieved with this method, 59% were actually similar and 37% were deemed exploitable for further processing. This is encouraging evidence for the target task of finding equivalent expressions between these two varieties of language. Keywords. Natural Language Processing, Consumer Vocabulary, Comparable Corpora