Yawning is a common physiological phenomenon, induced by hunger, sleepiness or impersonation. Its behavioral aim seems to be an effort to vigilance. There are numerous pathological reasons explaining yawning, as for example global (infectious, metabolic and toxical) or focal neurological diseases. The modification of yawning in pathology where a dopaminergic dysfunction is to be found, as well as some data of animal experimentation, support when it takes place the dopaminergic system's implication. The pre-synaptical receptor's role had been suggested for a long time but actually yawning seems to be linked with a D1-D2 cooperation. The cholinergic system probably control a final effective pathway. We also imply the peptidergic, serotoninergic, androgine and opiace systems. If the localization of a putative center of yawning is impossible, the nigrostriatal dopaminergic pathway, the paraventricular nucleus of hypothalamus and the pituitary gland play a major role. Yawning can be used as a functioning index of the dopaminergic system in vivo in the human being.