This year I started a new virology course at Columbia University. The course emphasizes the common reactions that must be completed by all viruses for successful reproduction within a host cell and survival and spread within a host population. The molecular basis of alternative reproductive cycles, the interactions of viruses with host organisms, and how these lead to disease are presented with examples drawn from a set of representative animal and human viruses, although selected bacterial viruses will be discussed. Each lecture is recorded as a videocast, which consists of slides and audio, and is made freely available for download. The lectures and reading assignments can be found at the course website: http://microbiology.columbia.edu/W3310.