There are many conventional microbiological methods in routine clinical practice to determine the sensitivity of common bacteria. The problem with these methods arises with bacteria that do not grow on habitual media (Rickettsia spp., Coxiella spp. and Anaplasma spp., among others) and for which there are no standardized techniques to determine their antimicrobial susceptibility. In addition, the techniques that are used for the culture of these fastidious bacteria show problems in both accuracy and reproducibility and, in some cases, the in vitro antimicrobial susceptibility of bacteria shows poor correlation with therapeutic outcome. Therefore, it becomes difficult to determine the antimicrobial drug susceptibility of some bacteria and, thus, to assess the therapeutic effect of drugs. The scientific breakthroughs that have taken place in recent years have allowed the use of new techniques that facilitate and improve microbiological study. This paper reviews the use of nuclear magnetic resonance spectroscopy as an alternative tool for determining antimicrobial drug susceptibility.