Ionic liquids (ILs) are chemical substances with good solubility and low vapor pressure because they are ionized and therefore charged. ILs may damage ecosystem due to their good water solubility. Toxicological studies for individual ILs. Major constraint in ILs ecotoxicology is that risk cannot be quantified by risk quotient methods because of unavailability of exposure assessment data. At present, only limited information is available about the impacts of ILs to aquatic ecosystems. The main objective of the current work is to use statistical methods to available literature on acute toxicity data of ILs to assess potential ecotoxicological risks when the ILs do come into industrial use. Probabilistic ecotoxicological risk assessment (PETRA) method was adopted by using Chemical Toxicity Distributions (CTDs) and Species Sensitivity Distributions (SSDs). SSDs has been used to derive threshold values below which the ecosystem and its biotic components could be protected from the adverse effect of ILs. CTDs has been used to estimate the probability of finding ILs with an effect below a calculated concentration which is considered to be safe environmental concentration. Acute toxicity data were collected from the literature on the acute toxicity of four bacterial pathogens Aeromonas hydrophila, Escherichia coli, Listeria monocytogenes and Staphylococcus aureus. CTD method was applied to assess the distribution of toxicities of group of IL to individual species. The SSD method was applied to estimate guideline values (GVs) to estimate different level of protection of bacterial species from ILs. Imidazolium chloride and bromide ILs were reported to pose more than 5 risk towards bacteria. Out of the four bacterial strains, E coli was reported to be potentially at higher risk because of highest sensitivity when exposed towards ILs. The risk posed was five percent which is acceptable level of risk. © 2018 Universiti Malaysia Pahang, Malaysia.