The aconite plants contain Aconitum alkaloids (AAs) and other minor components, such as chasmanine, kobusine and higenamine. AAs consist of aconitines, benzoylaconines and aconines as shown in Figure 1.1. The most toxic group is the aconitines, including aconitine, mesaconitine, hypaconitine, and jesaconitine; this group is one of the most poisonous compounds being contained in the plant kingdom. Even nowadays, aconite poisoning cases take place occasionally. These may be due to accidental, suicidal or homicidal ingestion of the plant itself or its extracts. In this chapter, a specific method for GC/MS analysis of AAs in human specimens is presented.