The European Food Safety Authority (EFSA) was asked by the European Commission to perform a risk assessment of neonicotinoids, including thiamethoxam, as regards the risk to bees. In this context the conclusions of EFSA concerning the risk assessment for bees for the active substance thiamethoxam 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 uses of thiamethoxam applied as a seed treatment on a variety of crops currently authorised in Europe. The reliable endpoints concluded as being appropriate for use in regulatory risk assessment, derived from the submitted studies and literature data as well as the available EU evaluations and monitoring data, are presented. Missing information identified as being required to allow for a complete risk assessment is listed. Concerns are identified.