OBJECTIVES: Despite the benefits of lipid lowering therapies (LLT), adherence to LLT remains poor. This review aims to summarize and assess evidence from prior research on the association between adherence to LLT and cholesterol outcomes (cholesterol levels and/or goal attainment). METHODS: We searched PubMed database for research articles written in English and published between January 1, 2000 and December 31, 2009 using combinations of the following terms: "adherence," "compliance," "statin," and "lipid lowering". Retrieved articles were included for review if they met the criterion of adherence/compliance as a predictor of cholesterol outcomes (e.g., LDL-C, HDL-C, or TC). RESULTS: The automated literature search yielded 527 studies, 8 of which met the inclusion criteria. Despite that a majority of studies examined adherence to LLT, only a few included cholesterol outcomes. A total of 519 studies were excluded: 340 for being off topic, 5 for having no adherence measure, and 174 for having no cholesterol measures reported as an outcome. This review initially sought to quantify the effect of adherence on cholesterol outcomes; however, adherence measures and methods varied greatly among the 8 studies and made data synthesis challenging. Heterogeneous methodologies were used for adherence measures, including medication possession ratio (MPR), medication event monitoring system (MEMS), adherence to therapy index (ATI), continuous measure of medication gaps (CMG) and pill counting. Regardless of how adherence was defined, better adherence was associated with improved cholesterol outcomes (lower LDL-C or TC or higher HDL-C levels compared to their respective baseline levels). CONCLUSIONS: Few studies evaluated both adherence to LLT and cholesterol outcomes and various methodologies were used for adherence measurements. Further studies assessing compliance and objective clinical endpoints are needed. Healthcare providers should monitor medication adherence and develop effective interventions to improve adherence given the evidence on improved cholesterol outcomes as a result of increased adherence.