Ionic liquids (ILs) have many potential applications in diverse fields because of their distinctive properties. The increasing interest in ILs in industrial and academic sectors is mainly due to recent demonstration of the close relationship between the compound structure and their properties, which could be modified for different purposes. ILs contain an inorganic anion and an organic cation, and different cations and anions could potentially be combined to create ILs for specific applications as, for example, bioseparation agents of active compounds (with special importance in petroleum industry), drug delivery systems, lithium ion batteries, paint additives, lubricants for high temperatures and low pressures and absorbents for heat pump devices. More than 30000 imidazolium-based ILs have already been included in the CAS database, and it has been estimated that more than 1012 different ILs could be synthesized. The vapour pressure of ILs is very low, and in some contexts ILs are considered innocuous because they are not harmful to the atmosphere. They are often referred to as "green fluids". However, their inocuousness has still to be proven, as the fact that they do not act as atmospheric toxins does not mean they are also harmless to aquatic and terrestrial environments. Furthermore, in case of accidental spillage, water-soluble ILs would quickly reach the soil surface in the surrounding area, as well as the deeper layers of soil and surface and subsurface waters. Moreover, given the large number of combinations of anions and cations and the lack of knowledge about the effects of IL structure on toxicity, it is not possible to generalize about the potential impact of ILs on the environment. The ionic liquid 1,3-dimethylimidazolium dimethylphosphate ([C1C1Im][DMP]) has many potential applications and is already used as, e.g., a lubricant-hydraulic fluid, an absorbent in heat pumps, a heat transfer fluid (in heaters or freezers) and a surfactant [3,5-6]. However, the toxicity of this IL to the soil remains to be investigated. This is especially important as soils with different characteristics, particularly in relation to organic matter (OM) and pH, may react differently to the presence of any exogenous compound. Ecotoxicology testing is often carried out with agricultural plants because these are sensitive to environmental stress and pollution. Seed germination and seedling development are crucial and particularly sensitive stages of plant development. If plants are grown in contaminated soil, the seeds and roots will be in direct contact with the pollutants, thus potentially affecting germination and/or plant development. Moreover, toxicity tests based on seed germination and elongation can be carried out with a wide variety of plant species that are radily available and also germinate and grow rapidly. The aim of this study was to investigate the toxicity of [C1C1Im][DMP] in soil by analyzing the germination and early development of seeds of one forest and one agricultural plant species in two different types of soil spiked in different compound concentrations.