Abstract
In case of general practitioners examinations of persons suspected problems with alcohol, illicit drugs or medicaments, laboratory analysis is often needed. Especially to proof unreliable statements, the laboratory analysis becomes very helpful. Therefore knowledge of laboratory analysis is necessary, particularly about testing blood and urin samples. Furthermore it is also very important to know the difference between direct markers with evidential character and indirect markers only as indicators. This article specially concerns laboratory analysis of the general practitioners assessing fitness to drive. (Author/publisher)