The EU Clinical Trials Directive came into force on 1 May 2004 and has changed the face of Clinical Trials of investigational medicinal products in the UK. An enthusiastic registrar or consultant who comes up with an idea for a therapeutic intervention now needs to comply with a complex and demanding set of legal, ethical and regulatory requirements, contravention of which may lead to criminal proceedings. The aim of this review was to detail the relevant procedures and regulations and to provide a 'user-friendly' guide to obstetricians and gynaecologists wishing to conduct a clinical trial of an investigational medicinal product. Sources of further information are listed.