Background: Advance care planning (ACP) provides patients with the ability to make their decisions known about how they would like to be treated if they lose capacity. Medical practitioners have a key role to play in providing information on ACP to their patients. This research explores their knowledge and attitudes to advance care planning and how this affects their practice. Aim: The objective of this study is to assess the NSW medical practitioners' knowledge and self-reported practice of ACP. Methods: A postal survey of a random sample of 650 general practitioners plus 350 medical specialists from specialties most often involved in end-of-life decisions was conducted. Respondents' work location post codes were subsequently used to assign respondents to one of the eight NSW Area Health Services. The main outcome measures were medical practitioners' knowledge of and practice pertaining to ACP. Results: Thirty-four per cent of specialists (n = 110) and 24% of general practitioners (n = 150) responded; the majority of respondents had heard of all ACP options. However, respondents' understanding of the uses and legal requirements of the relevant ACP options vary widely. Conclusions: Respect for patient wishes expressed in advance directives is reassuringly high. The findings suggest significant misunderstanding by medical practitioners of terminologies and systems around substitute decision-making for incompetent persons. Further education and standardisation of terminologies and systems across different jurisdictions would assist in addressing these issues. Low response rate, relating to only one legal jurisdiction, means results may not be generalisable.