Many of the challenges that banks face due to tighter margin requirements are still fresh and, in many cases, without solid industry consensus to guide their resolution. Yet the new margin rules are already in place and, in order to effectively trade in today's markets, financial institutions must quickly develop a keen understanding of the implications of, and techniques for, trading with large margin requirements. This is, therefore, a serendipitous time to organise the many strands of margin-related challenges into a coherent framework, and, more importantly, to present the thinking and research on these problems by a collection of leading academics, practitioners and regulators.