Disease resistance is a major goal in breeding new varieties and plays a key role in vegetable crop production and integrated pest management practices. It is also carefully described to differentiate new varieties from older ones on the market. The objective of the International Seed Federation Working Group on Disease Resistance Terminology is to promote the consistent use of terminology in relation to disease resistance. The Working Group codes pathogens for which companies claim resistance in their varieties, promotes harmonized terminology across the industry to avoid any liability due to miscommunication, develops host differentials and establishes procedures based on peer-reviewed scientific publication and industry practices to identify pathogen races/strains. To support the decision process associated with the nomination of novel races, the Working Group has formulated recommended guidelines. The recommendations constitute the minimum criteria to be fulfilled in order to nominate a novel race for a specific plant pest. An important selection criteria is the economic importance of the emerging resistance breaking event. The pest caused significant economic damage, the extent of this event is significant and the event is recurrent and observed over multiple growing seasons and/or years. The guidelines include basic rules for nomination and numbering of novel races. The nomination criteria and examples of numbering and differentials will be presented.