Health care today is characterized by an increasing number of patients with comorbidities for whom interphysician collaboration seems very important. We reviewed the literature to understand what factors affect interphysician collaboration, determine how interphysician collaboration is measured, and determine its effects. We systematically searched six major databases. Based on 63 articles, we identified five categories that influence interphysician collaboration: personal factors, professional factors, preconditions and tools, organizational elements, and contextual characteristics. We identified a diverse set of mostly unvalidated tools for measuring interphysician collaboration that focus on information being transferred and understood, frequency of interaction and tone of the relationship, and value judgements about quality or satisfaction. We found that interphysician collaboration increased clinical outcomes as well as patient and staff satisfaction, while error rates and length of stay were reduced. The results should, however, be interpreted with caution, as most of the studies provide a low level of evidence. Keywords: systematic review, interphysician, collaboration, Physician, medical specialist, hospital