Introduction: The comorbidity is a phenomenon that complicates general doctor´s fulfillment of their functions regarding the care of patients at Internal Medicine Wards. Objective: To base the bases of comorbidity as a variable, insofar it is defined in the conceptual, the operational and essential internal-external relationships with a systemic approach of the functions of the clinical physician in the hospital´s Internal Medicine wards. Material and Methods: A bibliographic revision that take into account comorbidity and allow to satisfy the objective was performed. Development: Conceptually, comorbidity is defined as the association of diseases in which one has a leading role character. The conceptual definition of comorbidity is presented. The relationship between comorbid diseases can be explained by associations of a clear pathogenic dependence or by coincidence in the patient without direct pathogenic relationship. There are numerous and diverse instruments available to make it operable for its application in research and clinical practice. Conclusions: The relations between different diseases are multilateral and need a deep etiopathogenic and fisiopathological interpretation to be understood and examined in the fulfillment of its asitencials, investigative, teaching and administrative functions of the doctor at Internal Medicine wards. Keywords: comorbidity, multipathology, internal medicine, clinical </p
