ESDU 91011 provides an estimation method for boiling heat transfer of multi-component mixtures, based on the method in ESDU 85041 for a single-component flow. After a discussion of the unique features introduced in mixture boiling, caused by the quality change as the lightest component vaporises, a step-by-step calculation procedure is given to obtain the heat flux or the length of tube to vaporise a certain proportion of liquid. A detailed worked example illustrates the use of the method. The accuracy of the predictions is briefly discussed on the basis of limited available measurements and the accuracy of the method for single-component flow.