‘Vanishing Viper 2019’ was organised in the wake of continuing evidence for declines in British populations of the northern viper or adder (Vipera berus). The meeting included British participants as well as those from other European countries, whose insights suggest that the drivers of adder declines in mainland Europe are similar to those in Britain. Consequently, we stand to benefit from their knowledge and experience. It was concluded that if adder declines continue at the present pace then Britain may be left with a few large, flourishing populations, but that many of the smaller populations will be lost as appears to have happened in Belgium, France, Germany and The Netherlands. The meeting considered a range of conservation actions including improvements to habitat management, the creation of adder ‘ARKs’, population restoration by genetic or demographic enhancements, community level promotion and outreach, and opportunities for new policy-driven environmental schemes. It is recommended to create a national Adder Working Group to help crystallise and prioritise the main issues and a larger, more informal Adder Network to link and co-ordinate adder researchers and land managers to ensure a free fl ow of ideas, information and advice. Our chances of success in these ventures will be all the greater if we continue to share experience with our European neighbours.