The question of whether self-archiving of preprints and/or postprints by journal authors is likely to have a significant impact on journal subscription numbers is currently a hotly debated issue of considerable policy importance for scholarly publishers. The moves by funding bodies and some institutions to request or require authors to deposit postprints has given more urgency to this issue as the archives are now likely to grow in number and more importantly in their content. This study was commissioned by ALPSP to ascertain what are the major factors contributing to journal cancellations, and thus to provide some new information for a debate that has inevitably so far been short of data. The study consisted of an online questionnaire. The wording was originally developed by ALPSP and Mark Ware Consulting, and then subject to review by a number of experienced librarians. The sample was obtained by posting requests to a number of listservs such as liblicense and SerialST. The sample was thus a self-selected one from a non-random group (those who chose to join the listservs) and this does represents a limitation of the study. Nonetheless a good response of 340 completed questionnaires was received, which we roughly estimate represents a response rate of 4-7%, perhaps reflecting the degree of interest in the topic.