Liquid fuels, such as gasolines and jet and diesel fuels, are usually refined products from the processing of crude oil. Their composition is mainly based on major physical properties and combustion performance indexes. For these reasons, real transportation fuels contain thousands of compounds that greatly vary with the feedstock origins, the seasons, and the economic factors that are imposed by the refinery. Regardless of this complexity, the chemical species contained in the fuels belongs to only four hydrocarbon classes: linear or branched alkanes, alkenes, cycloalkanes, and aromatics. Moreover, the physical properties ( such as vapor pressure and flash point) and the combustion properties ( such as octane or cetane numbers and smoke point) are regularly variable with composition. On these bases, it is viable to define surrogate mixtures to reproduce the most important chemical and physical properties of real transportation fuels. These surrogate fuels are then very useful both for the design of more reproducible experimental tests and for the development of reliable kinetic models, which are always projected to a deeper understanding of combustion processes. This paper analyzes some critical features in the definition of surrogates and in the development of detailed kinetic schemes of the pyrolysis and combustion of liquid fuels and also discusses experiments and simulation results obtained under very different conditions. These examples not only relate to ideal reactors ( such as plug flow, jet stirred, shock tube, or rapid compression devices), but also concern the knock propensity of hydrocarbon mixtures in internal combustion engines as well as the combustion behavior of liquid fuel droplets and the structure of premixed and diffusion flames.