Process plant design evaluations based on deterministic calculations do not take into account the uncertainties that are associated with the different input variables and the incompleteness of the different mathematical models used in the Row sheet program. The probabilistic simulation method was applied on an LNG (Liquefied Natural Gas) baseload plant design to obtain an impression of how some of these inaccuracies influenced a process plant design. The influences of the inaccuracies in vapour-liquid equilibrium K-values and enthalpy were examined. Key input variables were found to be K-values for methane and ethane along with the residual internal energy term in the enthalpy equation.