Listeriosis, (i.e. systemic infection caused by Listeria monocytogenes) is a notifiable disease in Australia and is almost always acquired by eating foods contaminated with the pathogen. Outbreaks have been associated with foods that are usually refrigerated, ready-to-eat and with a long shelf-life. Currently Food Standards Australia New Zealand is investigating changing the criteria for L. monocytogenes limits to align with international (Codex) standards for two broad categories of ready-to-eat foods: those in which growth can occur, and those in which growth will not occur. The change in criteria is dependent on their capacity to support growth of the organism or not. This presentation will provide an overview of modelling of the ecology of L. monocytogenes in foods and the use of challenge studies to evaluate whether ready-to-eat foods will support the growth of L. monocytogenes.