Strongly interacting quarks, anti-quarks and gluons are confined to hadrons at low energies, whereas a deconfining phase transition to a new phase of matter occurs at higher energies. In the early stages of relativistic heavy ion collisions such high temperatures are achieved and the Quark Gluon Plasma (QGP) is produced. As it turns out, predicitions based on ideal that is non-viscous hydrodynamics agree surprisingly well with experimental results. This agreement is slightly improved by including viscous effects. Transport coefficients characterizing these lowest order viscous effects are the shear and bulk viscosities. I will talk about how kinetic theory and in particular the Boltzmann equation can be used to perturbatively calculate the transport coefficients of QGP to leading order in the strong coupling constant.