To report on the response rate achieved in a survey of medical practitioners and discuss the reasons for it. An on-line (internet-based) survey of all 609 registered pharmacotherapy prescribers in Victoria and Queensland; invitations to participate were sent by mail in late April 2007, and one reminder letter in late May 2007. Six hundred and nine invitation letters were mailed, nine were returned to sender, and 52 questionnaires completed, making the overall response rate 52/600 = 8.7%. The response rate in Queensland was 13.2% (16/121), and in Victoria 7.5% (36/479). Despite utilising sound techniques, our response rate was much lower than those achieved in recent Australian paper-based surveys of medical practitioners. It is possible that the issue being addressed (injecting-related injuries and diseases) was not of high priority for many invitees, leading to reduced response. On-line surveys are not yet an effective method of collecting data from Australian medical practitioners; researchers should continue to use paper questionnaires for maximum response.