Information Systems outsourcing is a growing phenomenon in present-day firms that has generally been characterised with an insufficient level of detail and analysis. This is mainly due to the fact that outsourcing has been studied as a set of homogeneous services, failing to distinguish that there is a variety of contracts and ways to implement the outsourcing relationship. That is why this paper seeks to focus on all the aspects which define outsourcing contracts and relationships through the results of a survey carried out among the largest Spanish firms. An in-depth study has been performed, not only of the most often outsourced activities, but also of other attributes which capture the essence of the different outsourcing contract: the IT Outsourcing Configuration. A longitudinal study of many of these attributes is proposed that will help to foresee the future of IT outsourcing.