Abstract: The current number of problem opioid users in Europe can be estimated atabout 1.4 million, or 0.41 % of the adult population, with heroin being by far the most widely used opioid. Heroin use has developed along different timelines; several western European countries faced increases from the 1970s onward, whereas countries in Central and Eastern Europe saw a development in heroin use in the 1990s and later. Recent analyses of multiple indicators suggest that Europe may be witnessing a longer-term decline in heroin use, although countries show varying patterns and trends.