OBJECTIVES:  The MOSAIc study is a 2-year prospective observational study of patients with type 2 diabetes treated with insulin across 18 countries in 5 geographic regions. Insulin use patterns vary by region. This analysis describes treatment regimen changes from baseline to the end of study by region. METHODS:  Patients with type 2 diabetes, aged ≥18 years, and taking insulin for ≥3 months were included. Clinical, demographic, psychosocial, and health system data were collected within the routine course of care in each country. Treatment regimens at baseline and the end of study were compared, and the proportion of patients adding or switching treatments were analyzed by region, with emphases on basal (N=1,463) and premixed insulin (N=959) groups. RESULTS:  During follow-up, 78% of the basal group patients continued the same therapy, with regional variations from 66% in the Middle East (ME) to 83% in Latin America (LA). Adding different insulin was observed in 6% overall but was 4% for Europe (EU) and 9% for North America (NA) (p=0.04). In addition, 18% added a noninsulin therapy, ranging from 11% in NA to 27% in ME (p<0.01). In the premixed group, 79% of patients continued the same therapy, with regional variations from 73% in ME to 93% in EU. Adding different insulin was observed in 6% patients overall but was 4% in EU and 9% in LA and ME. In addition, 16% added a noninsulin therapy, with regional variation from 4% in EU to 18% in ME and Asia (p<0.01). CONCLUSIONS:  These data confirm differing patterns of insulin use by region and a relatively higher reliance on noninsulin therapy as insulin adjuncts over a 2-year period. Further work is underway to evaluate the outcomes associated with these care patterns and the underlying cultural, clinical, and health system factors that drive these differences.