OBJECTIVES: Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin  (JUPITER) demonstrated a statin benefit for primary prevention.  However, real-world patients may not exhibit medication persistence and adherence seen in the trial.  We described persistence and adherence of first-time statin users.  METHODS: A 10% random sample of the IMS LifeLink Health Plan Claims Database was used to obtain prescription claims records for adult (≥18 years) first-time statin users with continuous health plan eligibility 12 months prior and 32 months after the index statin prescription between July 1, 1997 and December 31, 2008.  Persistence and adherence were measured during the 24 months after statin initiation.  Patients were persistent if gaps in statin use did not exceed 180 consecutive days.  Adherence was measured as the medication possession ratio (MPR) during the period of persistence.  Persistence groups were categorized as ‘short’ (<9 months), ‘intermediate’ (9-16 months) and ‘long’ (17+ months) and compared using ANOVA.  RESULTS: Among 26,530 new statin users, the mean length of persistence was 17 months.  The proportions in each persistence category were: 21% ‘short’, 12% ‘intermediate’ and 68% ‘long’.  32% were persistent for 24 months or more, as compared to 75% of JUPITER patients taking medication after the median 1.9 year study period.  Mean MPR of the ‘intermediate’ and ‘short’ persistence categories were similar (0.70 vs. 0.69, P=.15), but lower than the overall mean MPR of 0.80.  Mean MPR was greatest in the ‘long’ persistence category (0.85, P<.0001) and was higher than the overall mean MPR.  CONCLUSIONS:   Persistence and adherence measure two different but critical concepts: the length of time patients use statins and their adherence to the statin regimen during that period, which we found to vary.  Extrapolating the primary prevention benefits of statins must account for both measures, as they differ from clinical trials to practice.