The expanding body of regulation to address occupational health and safety risks does not inevitably lead to improved health and safety outcomes if regulation is not enforced properly. This paper uses an economic approach to establish what are cost-effective techniques (inspection, education, sanctions) to enforce occupational health and safety regulation. The paper argues that proactive inspections play a crucial role and should be given priority in enforcement work. At the same time, it identifies conditions under which proactive inspections may prove cost-effective as well. The paper addresses the issue of post-detection discretion and holds that there are sound economic reasons for granting labour inspectorates such discretion. It analyses what role criminal law should play in enforcement of occupational health and safety regulation, particularly when compared to the less stringent systems of administrative penalties. It is argued that for most cases administrative penalties are sufficient to ensure deterrence and compliance whereas criminal law may well play an important residual role under certain circumstances, which the paper specifies. The paper briefly considers the role of complementary sanctions such as naming and shaming and addresses the role that third parties could play in enforcement of occupational health and safety regulation.