A formal comparison of physician notes on HIV patients with MEDCIN was carried out. Terms from patient charts were divided into five groups: History, Physical Examination, Symptoms, Diagnosis and Doctor's Orders. Four types of matches were determined: Exact, Lexical, Semantic and No-Match. Across the five groups, exact matches ranged from 12 to 44 percent, lexical matches from 2 to 11 percent, semantic matches from 9 to 21 percent, and no-matches from 29 to 74 percent.