This study explored the reasons general practitioners (GPs) are reluctant to participate in a postal survey. A cross-sectional postal survey was conducted among currently practising GPs in New South Wales, Australia, in 2002, who were asked to complete a questionnaire on the management of sexually transmitted infections (STIs). The overall response rate for the main STI survey was 45.4%. The GPs who did not respond to the STI questionnaire were sent a one-page non-response questionnaire asking them to report their reasons for not participating in the STI survey. Of the 491 non-responding GPs, 116 (23.6%) completed the non-response questionnaire and form the basis of the present paper. The key reasons reported by GPs for not participating in postal surveys were acute time constraints imposed by increasing workload including substantially increased paperwork, receiving too many survey requests, low STI caseload, and few incentives or returns on their time spent on completing surveys. While researchers need to be cognisant of constraints in general practice, it is also important to develop strategies for increasing GP involvement in research activities. To help improve participation of GPs in postal surveys, we recommend involvement of GPs in the design and conduct of research on issues relevant to general practice along with provision of feedback of survey results.