To investigate general dental practitioners' current understanding and practice of oral antibiotic prophylaxis. Cross-sectional survey of a random sample of New Zealand general dental practitioners (GDPs). A postal questionnaire was sent to 700 GDPs (response rate 64.5%). Most practitioners (91.3%) followed the guidelines of the National Heart Foundation of New Zealand (NHFNZ), rather than those of other organisations, and the majority accurately prescribed the standard oral amoxycillin dose. However, there was inconsistency when prescribing for penicillin-allergic patients, with three-quarters of respondents opting for inappropriate regimens, and almost half favouring an outdated erythromycin regimen. There was also inconsistency in prescribing for patients with a prosthetic joint. Most respondents considered their practice to be adequately equipped to handle an allergic reaction. In general, New Zealand GDPs adhere to the accepted guidelines for antibiotic prophylaxis, but some confusion remains, and a review of the NHFNZ guidelines may be warranted to ensure that they reflect current scientific opinion, and to make New Zealand guidelines consistent with those used in similar countries.