To identify factors affecting bulk-billing by general practitioners in Australia.A community-based survey was administered to Australians aged 16 years or older in July 2013 via an online panel. Survey questions focused on patient characteristics, visit characteristics, practice characteristics.Factors associated with GP bulk-billing.2477 respondents completed the survey, of whom 2064 (83.33%) reported that the practice that they went to for their most recent GP visit bulk billed some or all patients. Overall, 1763 respondents (71.17%) reported that their most recent GP visit was bulk billed. Taking into account the duration of visits and the corresponding Medicare Benefits Schedule rebate, the mean out-of-pocket cost for those who were not bulk billed was $34.09. RESULTS of a multivariate logistic regression analysis suggest that the odds of being bulk billed was negatively associated with larger practice size, respondents having had an appointment for their visit, higher household income and inner or outer regional area of residence. It was positively associated with the presence of a chronic disease, being a concession card holder and having private health insurance. There was no association between bulk-billing and duration of GP visit, age or sex.Our results indicate that there are associations between patient characteristics and bulk-billing, and between general practice characteristics and bulk-billing. This suggests that caution is needed when considering changes to GP fees and Medicare rebates because of the many possible paths by which patients' access to services could be affected. Our results do not support the view that bulk-billing is associated with shorter consultation times.