The European Food Safety Authority (EFSA) was asked by the European Commission to perform an evaluation of imidacloprid as regards the risk to aquatic organisms. In this context the conclusions of EFSA concerning the risk assessment for aquatic organisms for the active substance imidacloprid are reported. The context of the evaluation was that required by the European Commission in accordance with Article 21 of Regulation (EC) No 1107/2009 to review the approval of active substances in light of new scientific and technical knowledge and monitoring data. The conclusions were reached on the basis of the evaluation of the representative uses of imidacloprid authorised at the time of approval of the substance. The proposed endpoints concluded as being most appropriate for use in regulatory risk assessment, derived from the submitted studies and literature data, are presented. Missing information identified as being required to allow for a complete risk assessment is listed.