Poliomyelitis (polio) is a highly infectious disease that affects mostly young children and which may lead to paralysis and death. Prevalence of polio has considerably decreased. However, the effort of global eradication through immunisation needs to be continued to prevent infection risks in non-vaccinated populations by wild, as well as vaccine-derived, polioviruses. In addition, the stockpile of oral poliomyelitis vaccine (OPV) must be maintained for emergency cases even after eradication. To this end relevant reference standards must be available for the quality control (QC) of polio vaccines. Stocks of the European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) batch 3 for the assay of OPV are dwindling and therefore a collaborative study was initiated by the European Directorate for the Quality of Medicines and HealthCare (EDQM) with the goal to establish a replacement batch as a working standard. Ten laboratories took part in the collaborative study to calibrate the candidate BRP (cBRP), a commercial trivalent OPV containing live attenuated poliovirus types 1, 2 and 3 (Sabin strain), against the WHO 2nd International Reference Reagent (IRR) for OPV and, for the sake of continuity, to compare it to the BRP batch 3. Based on the results of the collaborative study, the cBRP appears suitable as a reference standard and the potencies assigned are 7.28, 6.34, 7.01, and 7.52 log10CCID50/mL (CCID50: 50 % Cell Culture Infective Dose) for poliovirus type 1, 2 and 3 and for the total virus content respectively. The cBRP was adopted by the Ph. Eur. Commission at its 146th session in June 2013 as Ph. Eur. BRP batch 4 for OPV.