[ABSTRACT] One of the trait that define the bipolar disorders is their natural evolution. The study of this trait has a primordial interest to the clinician. Starting from this point the author analyzes the different aspects of the course of the illness like the stages of the manic episode, the age of onset, the number of episodes to be expected, the cycle types, the seasonal presentation of the phases, the expected length, the long term evolution, etc.Una de las características que definen a l