Particles are the building blocks from which events are constructed. We here use the word `particle' in its broadest sense, i.e. including partons, resonances, hadrons, and so on, subgroups we will describe in the following. Each particle is characterized by some quantities, such as charge and mass. In addition, many of the particles are unstable and subsequently decay. This section contains a survey of the particle content of the programs, and the particle properties assumed. In particular, the decay treatment is discussed. Some particle and decay properties form part already of the hard subprocess description, and are therefore described in sections , and .