Increasingly, academic libraries are investing heavily in e-journals which duplicate their print back-runs. For libraries facing acute pressures on space, one solution to their problem is to dispose of or relegate print back-runs which overlap with their electronic holdings. This case-study focuses on work at Imperial College London Library to provide a tool-kit for staff making such deselection decisions. Imperial has established criteria to determine the sustainability of their e-journals. A purpose-built database has been developed to store data on sustainability and enable staff easily to identify the overlap between print and electronic holdings at each Library site. Librarians at Imperial are now using the database and have already identified 700 metres of print journals with sustainable electronic access for disposal.