The entire collection of 11.5 million MEDLINE abstracts was processed to extract 549 million noun phrases using a shallow syntactic parser. English language strings in the 2002 and 2001 releases of the UMLS Metathesaurus were then matched against these phrases using flexible matching techniques. 34% of the Metathesaurus names (occurring in 30% of the concepts) were found in the titles and abstracts of articles in the literature. The matching concepts are fairly evenly chemical and non-chemical in nature and span a wide spectrum of semantic types. This paper details the approach taken and the results of the analysis.