Following a request from the EU Commission, the Panel on Plant Health has addressed the pest categorisation of non-EU isolates of potato virus X (PVX). The information currently available on geographical distribution, biology, epidemiology, potential entry pathways, potential additional impact and availability of control measures of non-EU isolates of PVX has been evaluated with regard to the criteria to qualify as a potential Union quarantine pest. Because non-EU isolates of PVX are absent from the EU, they do not meet one of the requirements to be regulated as a regulated non-quarantine pest (RNQP) (presence in the EU); as a consequence, the Panel decided not to evaluate the other RNQP criteria for these isolates. On the basis of their ability to overcome potato resistance genes, PVX isolates can be divided into several pathotypes. PVX isolates that are not able to overcome resistance genes and PVX isolates that are able to overcome the Nb and/or Nx resistance genes are already present in the EU. Isolates able to overcome the Rx resistance gene have only been reported from South America. These Rx breaking isolates could potentially have an additional impact over the current situation in the EU and therefore meet all the criteria to qualify as a potential Union quarantine pest. All other non-EU isolates, should they be introduced, are not expected to have additional impact and therefore do not meet this criterion to qualify as a potential Union quarantine pest.