African horse sickness (AHS) is an acute insect-borne viral disease of horses and other equines causing depression, respiratory and circulatory impairment. The mortality rate may approach 100%. The disease is transmitted by midges. In 2007–2009 midges caused the spread of bluetongue in cattle and sheep in Northern Europe. The midges are also the main vector and transmitter of AHS and the disease may occur in horses in the Nordic Baltic region during summer or early autumn. Contingency plans covering AHS have been adopted by the Nordic Baltic countries. This report provides information on the preparatory work and the conduct of a simulation exercise. The aim of the exercise included testing of National AHS contingency plans and of the communication systems established between veterinary authorities in the Nordic and Baltic countries for animal disease emergencies.