This presentation details the methods and applications of applying MR spectroscopy (MRS) to living organisms, especially to humans, for diagnosing pathological processes or even predicting outcome of therapeutic measures. The task of in vivo MRS is the detection of metabolites of low concentrations within a clinically feasible acquisition time. With single “voxel” spectroscopy (SVS), a single spectrum from a defined location is acquired; chemical shift imaging (CSI) or spectroscopic imaging (SI) refers to the simultaneous acquisition of multiple voxels. At least eight phase cycles are required to selected the desired echo of a three-pulse sequence. The frequency domain signal area which is correlated with metabolite concentration becomes independent of field homogeneity. A minor additional advantage of the spinecho sequence is a lower sensitivity against diffusion, due to shorter intervals between spoiling gradient pulses. When used for detection proton signals, these SVS techniques are used in combination with a water suppression sequence module. Chemical shift imaging is discussed. CSI sequences mostly rely on phase-encoding as it is known from imaging sequences, for resolving the metabolite concentrations from multiple voxels. The volume selected by the slice selective pulses covers a region of interest of the inner brain which is further resolved by phase encoding, while the selection of intense subcutaneous or bone lipid signals can be avoided. Using multiple element receive “matrix” coils, the sensitivity of clinical MRS can be substantially increased. The goal of fast CSI techniques is to reduce the minimum measurement time. The task of MRS post-processing is to evaluate at least relative metabolite concentrations and to display results. It appears hardly possible to device a general purpose algorithm for absolute metabolite quantitation, due to a number of parameters usually not determined during a clinical MRS exam, and due to the fact that a ground truth for verifying in vivo results is hardly available.