Diabet. Med. 29, e88–e95 (2012) Aim  In Germany, regional data on the prevalence of Type 2 diabetes mellitus are lacking for health‐care planning and detection of risk factors associated with this disease. We analysed regional variations in the prevalence of Type 2 diabetes and treatment with antidiabetic agents. Methods  Data of subjects aged 45–74 years from five regional population‐based studies and one nationwide study conducted between 1997 and 2006 were analysed. Information on self‐reported diabetes, treatment, and diagnosis of diabetes were compared. Type 2 diabetes prevalence estimates (95% confidence interval) from regional studies were directly standardized to the German population (31 December 2007). Results  Of the 11 688 participants of the regional studies, 1008 had known Type 2 diabetes, corresponding to a prevalence of 8.6% (8.1–9.1%). For the nationwide study, a prevalence of 8.2% (7.3–9.2%) was estimated. Prevalence was higher in men (9.7%; 8.9–10.4%) than in women (7.6%; 6.9–8.3%). The regional standardized prevalence was highest in the east with 12.0% (10.3–13.7%) and lowest in the south with 5.8% (4.9–6.7%). Among persons with Type 2 diabetes, treatment with oral antidiabetic agents was more frequently reported in the south (56.9%) and less in the northeast (46.0%), whereas treatment with insulin alone was more frequently reported in the northeast (21.6%) than in the south (16.4%). Conclusion  The prevalence of known Type 2 diabetes showed a southwest‐to‐northeast gradient within Germany, which is in accord with regional differences in the distribution of risk factors for Type 2 diabetes. Furthermore, the treatment with antidiabetic agents showed regional differences.