BACKGROUND AND AIMS: Real-world data on treatment patterns in Japanese hyperlipidemia patients with diabetes mellitus (DM) or prior atherosclerotic cardiovascular diseases (ASCVD) are lacking. METHODS: This is a retrospective, longitudinal cohort analysis of administrative claims data (Japan Medical Data Center [JMDC] and Medical Data Vision [MDV] databases) for patients prescribed a new hyperlipidemia medication between 2014 and 2015. Patients were followed for >/=12 months. Outcomes included prescribing patterns, persistence (discontinuations), and adherence (proportion of days covered). RESULTS: Data were analyzed for 11,718 and 27,746 DM, and 4101 and 14,356 ASCVD patients from the JMDC and MDV databases, respectively. Among previously-untreated patients, index prescriptions were primarily for moderate statins in the DM (JMDC: 74.7%, MDV: 77.5%) and ASCVD (JMDC: 75.4%, MDV: 78.5%) sub-cohorts. Combinations were rarely prescribed (=2.5%). Previously-treated patients were most frequently prescribed combinations in the DM (JMDC: 46.7%, MDV: 53.6%) and ASCVD (JMDC: 49.3%, MDV: 53.3%) sub-cohorts. Intensive statins were rarely used by previously-untreated (=1%) or previously-treated (=8%) patients in either sub-cohort. Approximately half of previously-untreated patients discontinued hyperlipidemia therapy within 12 months. Adherence was >/=80% across most drug classes. CONCLUSIONS: Many Japanese hyperlipidemia patients with DM or ASCVD are prescribed single-agent lipid-lowering therapy. Use of intensive therapy is lower than expected, and is suggestive of under-treatment. The low persistence rates are concerning, and warrant further study.