European Carp is a species of freshwater fish that live in Australia's freshwater rivers, wetlands and lakes. It is a dominant pest species in Australia. As part of investigations into the potential release of the Cyprinid Herpes Virus 3 to control Carp numbers, a Choice Modelling (CM) study was undertaken to value the potential non-market environmental benefits of such a program. These potential benefits relate to increases in native fish populations, the area of healthy wetlands and waterbird populations. The CM study explicitly included a probability attribute to reflect the risk that various release options will deliver the identified environmental outcomes. Consequently, the willingness to pay (WTP) estimates derived from the choice models are expressed in terms of the expected values of outcomes: the physical outcomes multiplied by their probabilities of occurring. The preferred model of choice was a Random Parameter Logit model with a non-linear (cubed) transformation of the levels for each probability weighted environmental attribute. Consequently, estimates of WTP derived from the model increase as the level of an expected attribute increases. This non-linear form is consistent with respondents treating risk in a nonlinear fashion.