This paper describes the present situation regarding chemical kinetic databases for the simulation of the combustion of liquid fuels. Past work in the area is summarized. Much is known about the reactions of the smaller fragments from combustion processes. In order to describe real liquid fuels there is the need for an understanding of how the larger organic fuels are broken down to these fragments. The type of reactions that need to be considered are described and the breakdown of heptane is used as an example.