Information System (IS) evolution is today a continuous preoccupation of every modern organization that aims to have a perfect support for its constantly changing business ecosystem. However, the task of IS evolution is not anodyne, it presents several risks towards IS sustainability as well as towards enterprise activity. Taking a decision related to any IS change can be a troublesome responsibility because of the amount of information that has to be processed and the uncertainty of the impact of the change on the enterprise and its IS. To reduce this uncertainty, we have developed a conceptual framework for IS evolution steering. This framework allows to capture the information on how enterprise IS supports its activities and regulations, and then to extract the information relevant for realizing IS evolution activities, simulating their impact, and taking appropriate decisions. This second part of the framework is called the responsibility space of IS evolution steering and is the main subject of this paper.