OBJECTIVE: The aim of this study was to determine the percentage of anti-hypertensive drugs documented in medical records that appeared in managed care pharmacy claims. METHODS: Study subjects were incident hypertensive patients identified by: 1) at least one claim with an ICD-9 diagnosis code of hypertension and at least one claim for an anti-hypertensive drug; or 2) at least two claims with an ICD-9 diagnosis code of hypertension, preceded by a six-month treatment free period. Nurse abstractors reviewed medical records for newly initiated or continuing anti-hypertensive drugs (ACE inhibitors, angiotensin II receptor blockers, beta-blockers, calcium channel blockers, and diuretics). To determine whether these drugs were filled, we reviewed pharmacy claims for a twelve-month period after the subject’s initial anti-hypertensive drug claim. Drugs were “filled as intended” if a pharmacy claim for the same drug was identified, and filled within seven days prior to, or 30 days after, the date of the notation in medical records. RESULTS: Medical records were abstracted for 563 patients, with 2,205 notations of newly initiated or continuing anti-hypertensive drugs. Of these, 1,209 (54.8%) pharmacy claims had fill dates that appeared to have been “filled as intended”. The median “days supplied” for these fills was 30 days, with a mode of 30 days. CONCLUSION: In this population, 54.8% of anti-hypertensive drugs noted in medical records appeared to have been “filled as intended” based on pharmacy claims data. Given a median of 30 “days supplied” for anti-hypertensive drugs, patients would be expected to have filled medications documented in medical records within the “filled as intended” time frame. This simple analysis further illustrates that patients frequently do not comply with medication taking for chronic, asymptomatic conditions.