The objective of this trial is to investigate the pharmacokinetics and pharmacodynamics of linagliptin (BI 1356) 5 mg administered orally in patients with Type 2 diabetes mellitus of African American origin.

Inclusion criteria:

1. Glycosylated haemoglobin >=7 and <= 10%
2. Age >=21 and <= 65
3. Body Mass Index >=18.5 and <=38 kg/m2
4. African American origin
5. Signed and dated informed consent prior to admission to the study

Exclusion criteria:

1. Any finding of the medical examination considered clinically relevant by the Investigator
2. Clinically relevant concomitant diseases like renal insufficiency, cardiac insufficiency New York Heart Association (NYHA) II-IV, known cardiovascular disease including hypertension >160-100 mmHg (under current treatment), stroke and transient ischemic attack (TIA).
3. Clinically relevant gastrointestinal, hepatic, renal, respiratory, cardiovascular, metabolic, immunological or hormonal disorders besides type 2 diabetes
4. Clinically relevant diseases of central nervous system or psychiatric disorders or relevant neurological disorders besides polyneuropathy
5. Diagnosis of sickle cell anemia or known chronic anemia
6. History of chronic or relevant infections (for example human immunodeficieny virus (HIV), Hepatitis B)
7. History of relevant allergy/hypersensitivity
8. Intake of drugs with a long half life (>24hours) within at least one month or less than 10 half lives of the respective drug prior to administration except allowed co medication
9. Alcohol abuse, drug abuse
10. Any laboratory value of clinical relevance that is outside an acceptable range
11. Change of drug dosing of allowed co medication
12. Any (electrocardiogram) ECG value outside the reference range and of clinical relevance.
13. Fasted glucose >270 mg/dl or randomly determined blood glucose >400 mg/dl on two consecutive days during screening or wash out
14. Serum creatinine above upper limit normal at screening