Molecular phylogenetic analysis is widely used by virologists to study the epidemiology and evolution of viruses. Many virologists that are using these methods lack a theoretical background and practical training often resulting in misinterpretation of results. In this workshop we will give a thorough training in the scientific background of molecular evolution, the elementary problems of molecular epidemiology and give the participants a perspective of which methods are available and what kind of information can be obtained from them. Participants will also be requested to present their own research data. In this way, trained virologists will be able to perform and evaluate molecular epidemiology, and will have contacts with other participants and with the workshop teachers to discuss the application of phylogenetic analysis for the specific epidemiological problems they encounter during their research.