Neonicotinoids bind to nicotinic acetylcholine receptors (nAChRs) of insects, and higher doses lead to receptor blockage, paralysis and death. They are selectively more toxic to insects than to vertebrates. Imidacloprid was the first available neonicotinoid. But soon after its introduction environmental concerns arose: for instance in France in 1994, when many hives collapsed after the application of imidacloprid on sunflowers. Neonicotinoids are highly soluble in water, they leach easily, significant levels can reach groundwater supplies, and run-off can take place after application. This leaching potential is a very important concern when neonicotinoids are used on fields near aquatic habitats. Aquatic invertebrates are particularly susceptible to pesticides. Fish are distinctly less vulnerable than aquatic insects. Aquatic insect larvae react even to low levels of imidacloprid. Growth, reproduction and survival of larvae decrease. This could have consequences for the individuals, for the population, and for the ecosystem, because insect larvae are food for insectivorous species. The toxicity of clothianidin, acetamiprid, thiacloprid and thiamethoxam ranges from zero to moderate for fish but they are highly toxic to aquatic invertebrates. Neonicotinoid insecticides offer many benefits for agriculture, but they are toxic to invertebrates, which have an important role in the ecosystem. However, as neonicotinoid insecticides are primarily applied prophylactically, they preclude the use of integrated pest management (IPM). IPM is an all-inclusive science-based approach to dealing with the challenges of agricultural pest control, which, among other efficiency goals, aims to minimize the use of chemicals by maximizing their effectiveness. Prophylactically insecticides are difficult to integrate into such a philosophy as they are applied preventively independent of local conditions.