Metabolite profiling has been established as a multiparallel strategy for relative quantification of a mixture of compounds or compound classes using chromatography and universal detection technologies (gas chromatography-mass spectrometry [GC-MS], liquid chromatography-MS). Despite its origins dating back to the late 1960s, it was only in the 1980s that its use was acknowledged to diagnose metabolic disorders in men, especially for rapid screening of inborn errors. Even faster electrospray ionization-MS/MS screening methods replaced longish chromatographic methods, and method development had stopped despite its potential use for other, less imminent diseases such as likelihood assessments of type II diabetes mellitus or cardiovascular risk factor evaluation. In addition to its diagnostic use, profiling blood samples can be employed to investigate specific biochemical responses. The broader scope of analysis outweighs the disadvantages by taking compromises in method development and the reduced accuracy for specific metabolites. This chapter exemplifies the strategies in metabolite profiling by GC-MS. It gives experimental details on basic steps like blood plasma withdrawal, storage, protein precipitation, extraction, concentration, derivatization, data acquisition, raw data processing, and result data tranformation. A major difference to profiling plant tissues is that no fractionation step is utilized, enabling the analysis of primary metabolites like sugars and amino acids concomitant with lipids such as sterols and free fatty acids.