Category 0 vocabularies in UMLS metat...

There were 43 Category 0 vocabularies in the January 1, 2003 release of the UMLS metathesaurus. Several of the largest and most useful Category 0 vocabularies are:

MESH (Medical Subject Headings) – 516,793 terms

National Center for Bioinformatics Taxonomy – 136,466 terms

LOINC (Logical Observations Identifiers, Names and Codes) – 79,522 terms

MTHICD9 – NLM-generated entry terms for ICD-9 18,507