Objective: to characterize the relationships between Insurance Companies and hospitals within the contracting out process. 
 Methodology: an exploratory study was conducted, involving twenty-nine officials from several health institutions located in Medellín city. The recollection of the information was made through semiestructural interviews based on a guide. The analysis of information was made following the coding criteria proposed by Huberman and Miles. It was developed in three steps, through which descriptive, analytic and interpretative categories emerged. 
 Results: findings suggest that hospitals have carried out administrative transformations in order to improve and maintain within a market environment. The health insurance companies achieve a dominant position between the actors of the health system, which is expressed through out the contracting out process, with imposition of tariffs and conditions to the contracts. 
 Conclusions: there is unbalance in power of actors, within which, the health insurers dominate the contracting out process, which generate conflicts between actors.