Publications concerned with the heat processing of foods stress the importance of factory management and operatives strictly complying with scheduled heat processes, but there is limited coverage in technical publications of the details of procedures for monitoring heat transfer in products and the many considerations which must be taken into account to avoid errors. The personnel required to carry out heat penetration trials often do not have access to practical information on this subject.Decisions on heat processing regimes are required for all new products, as well those in which there has been a change in formulation, manufacturing procedures or packaging type or shape. Routine checks on established lines are also good practice. This guideline addresses these issues, by focusing on the selection of heat process values, heat transfer characteristics, methods of evaluating processes and critical factors to consider when developing a heat processing regime. It is primarily aimed at in-pack (metal, glass or plastic) sterilised foods and drinks (both high- and low-acid), but many aspects can also be applied to pasteurised products. It will serve as a vital source of information for staff with limited experience of this type of work, and as a useful reference document for more experienced operatives.