This study was undertaken to model and predict growth of Salmonella and the dominating natural microbiota, and their interaction in ground pork. Growth of Salmonella in sterile ground pork at constant temperature between 4 C and 38 C was quantified and used for developing predictive models for lag time,max. specific growth rate max. population density .Data form literature were used to develop growth models for the natural pork microbiota. Challenge test at temperature form 9.4 to 24.1 C and with Salmonella inoculated in ground pork were used for evaluation of interaction models.The existing Jameson-effect and Lotka-Volterra model performed better and appropriately described the continued but reduced growth of Salmonella after the natural microbiota had reached their max. population density. The expened Jamrson-effect model is a new and simple species interaction model, which performed as well as the more complex Lotka-Volterra model.