Rebels, militias and army units have hijacked the trade in mineral ores from eastern Democratic Republic of Congo (DRC), while subjecting the civilian population to massacres, rape, extortion, forced labour and forced recruitment of child soldiers. Congo’s `conflict minerals’ are laundered into the global supply chain by export houses, before being transformed into refined metals by large international smelting firms. The metals are then used in a wide range of products, including consumer electronic goods such as mobile phones and computers. Some of the world’s most famous brands are now coming under scrutiny to address their role in this devastating trade.Nobody forces companies to purchase minerals or metals mined in war zones. It is their choice. Those that source minerals or metals originating from eastern DRC need to show the public that they have procedures in place to prevent direct or indirect involvement with serious human rights abuses and other crimes. This is what is called `due diligence’.Despite the mounting pressure on companies that use minerals and metals to carry out due diligence, few are actually doing this. Some companies claim that it is too complicated or too difficult for them to do. Due diligence is a process that all reputable companies understand and employ on a regular basis to address risks ranging from corruption to environmental damage.This paper argues that the due diligence that companies using minerals or metals originating from eastern DRC needs to undertake consists of:• A conflict minerals policy• Supply chain risk assessments, including on the ground checks on suppliers• Remedial action to deal with any problems identified• Independent third party audits of their due diligence measures• Public reportingThe report outlines each of these elements and makes suggestions on how companies can put them into practice. By putting these measures in place, companies can help to create a mining sector in eastern DRC that brings real benefit to the people who live there. A due diligence-based approach to sourcing minerals and metals is not about imposing blanket bans on trade; it is about ensuring that business does not perpetuate armed violence, serious human rights abuses and other crimes.At the same time, a key message to companies that runs through this paper is that if they choose to use minerals or metals originating from eastern DRC they have a responsibility to demonstrate – by doing due diligence – that their activities are not causing harm. If they cannot do this, they must seek their supplies elsewhere.