It is current practice to represent and analyze vapor-liquid equilibrium data through the use of state conditions (temperature and pressure) and phase compositions. However, these representations do not reveal and identify the accuracy of the data for important purposes, such as separation by distillation-and this is particularly a problem for the important low concentration regions. The intent of this editorial is to present the guidelines of the Journal of Chemical & Engineering Data that vapor-liquid equilibrium data should be evaluated through the use of charts and related analyses that bring to light the low concentration regions, for example, K-values and relative volatilities.