The conclusions of EFSA following the peer review of the initial risk assessments carried out by the competent authorities of the rapporteur Member State, Belgium, and co-rapporteur Member State, Greece, for the pesticide active substance 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) are reported. The context of the peer review was that required by Commission Implementing Regulation (EU) No 844/2012. The conclusions were reached on the basis of the evaluation of the representative uses of 2,4-DB as a herbicide on winter and spring barley, wheat and oats, and on legumes (lucerne and clover). The reliable end points, appropriate for use in regulatory risk assessment are presented. Missing information identified as being required by the regulatory framework is listed. Concerns are identified.