High-resolution NMR spectroscopy is widely used for the determination of the structure of complex molecules and the quantitative analysis of multicomponent mixtures in solutions. In the past decade, the extremely rapid development of NMR instrumentation resulted in an increase in the resolution and sensitivity of instruments by more than an order of magnitude. This has opened up new opportunities for the use of NMR spectroscopy in the quantitative analysis of the most important biological fluids (urine, blood plasma, cerebrospinal fluid, saliva, bile, tears, etc.), each of them can contain to several thousands of components in micromolar or lower concentrations. Clinicians and biologists from many countries used new capabilities of NMR spectroscopy to develop efficient methods for metabolic studies, medical diagnostics, and the development of new pharmaceutical preparations. This review briefly describes the status of studies in this new rapidly developing area of analytical chemistry and summarizes some of our experimental results.