Under current European Union legislation, action to restrict the production and use of a chemical is only justified if there is evidence that the chemical poses a risk to human health or the environment. Risk is understood as being a matter of the magnitude and probability of specifiable harms. An examination of how risks from chemicals are assessed shows the process to be fraught with uncertainty, with the result that evidence that commands agreement as to whether a chemical poses a risk or not is often not available. Hence the frequent disputes as to whether restrictions on chemicals are justified. Rather than trying to assess the risks from a chemical, I suggest that we should aim to assess how risky a chemical is in a more everyday sense, where riskiness is a matter of the possibility of harm. Risky chemicals are those where, given our state of knowledge, it is possible that they cause harm. I discuss four things that make a chemical more risky: (1) its capacity to cause harm; (2) its novelty; (3) its persistence; and (4) its mobility. Regulation of chemicals should aim to reduce the production and use of risky chemicals by requiring that the least risky substance or method is always used for any particular purpose. Any use of risky substances should be justifiable in terms of the public benefits of that use.