This chapter highlights some applications of chemical ionization mass spectrometry (CIMS). CIMS should be considered as an additional method in the identification of some compound classes. The complexity of aroma concentrates, which contain hundreds of compounds in concentrations ranging from percent to µg/kg levels, has continuously forced flavor chemists to develop new techniques or to creatively use existing possibilities. The quality of a food product is ascertained by, among other things, its odor, that is, by the presence and the level of volatile compounds. Sensory evaluation of food and beverages is as old as humankind. Extraction with low-boiling organic solvents, often in combination with steam distillation, is frequently used in food flavor analysis. High-boiling, low-volatile compounds can be separated with gas chromatography at high temperatures or at lower temperatures after derivatization. The odor characteristics of volatile compounds are largely affected by their stereo structure, that is, by their geometric or optical isomerism.