This publication examines the enforcement of public health legislation. Its underlying theme is that enforcement is not necessarily the same as the prosecution of offences. Other compliance tools should also be available that achieve the goal of enforcing the law without prosecution being necessary. However it is also recognized that there will be instances where the only commensurate response to a failure to observe the law will be prosecution. The role and responsibilities of those officers authorized to collect evidence and bring cases to court are considered. Advice is included about the quality (standard) of evidence that must be attained in order for that evidence to allowed to be used in court. Otherwise the evidence will not be admissible. The conduct of a prosecution including advice on witness testimony is also addressed. By producing this guide The WHO Regional Office for the Western Pacific aims to give more visibility to the issue of enforcement of public health legislation. It is hoped that it will stimulate discussions between health and law experts policy-makers and enforcement officers so that public health enforcement will be better understood and supported. Effective and fair enforcement of public health law is a critical component of every government's responsibility to improve and protect the public health of all people in their country. The issues and processes discussed in this guide therefore should serve as a resource for both enforcement officers in the field and policy-makers when laws are being developed or amended.