This mission report describes the findings of two experts deployed by the UN Environment/OCHA Joint Unit (JEU) in Mongolia following a sodium cyanide chemical spill. A spill of sodium cyanide from gold mining activities in Khongor Soum in northern Mongolia took place in April 2007, polluting the ground, air and drinking water. It was feared that this incident could threaten 6,000 people and 60,000 animals. While no international assistance was requested as an immediate response to the toxic spill, in July 2007, Mongolian authorities requested the JEU to deploy an environmental expert to undertake a fact-finding mission on the accident and the national response to it, and to examine related environmental risks stemming from the mining sector. The expert found the soil to be contaminated with mercury and sodium cyanide, as well as the ground water, drinking water supplies and the wastewater treatment plant. Several recommendations were made to prevent further contamination, and to support response preparedness and capacity-building initiatives. Given the potential danger from chemical substances at the site and in Mongolia generally, the JEU received a further request for assistance for capacity-building. Two experts were hired by the United Nations Development Programme (UNDP) to train the emergency responders. The JEU also collaborated with the World Health Organization and UN Environment to ensure that follow-up technical support was provided.