Molecular diagnostics methods are not limited to specialized centers anymore. They play an important role for the diagnostic of infections commonly encountered in the clinical practice. Especially the detection of pathogens difficult to cultivate, such as viruses, has been greatly improved by these methods. Often, PCR has become the gold standard for the diagnostics of these pathogens. However, PCR cannot be used in any case, and it is not fail proof. Therefore, it is important to know when to use molecular methods and what are their strengths and weaknesses, in order to prescribe them rationally. This article reviews the characteristics of molecular tests and their main indications in the ambulatory setting.