The viral entry process presents multiple early barriers that a virus must overcome before it can infect a cell. Initially the virus binds to the cell surface via interaction with receptors at the host membrane. Often this involves specific or even multivalent viral proteinreceptor interactions which confer cell-type or even species specificity. Later, viral uncoating is necessary for the virus to release its genetic information. In enveloped viruses, which contain a lipid membrane surrounding the viral capsid, this is accomplished by a complex mechanism where viral fusion proteins catalyze the fusion between viral and host membrane. Even though these steps offer multiple vantage points for antiviral treatment, effective drugs are only available for a limited number of viral diseases. As such, mechanistic studies of viral binding and fusion carry large potential to uncover new routes to therapeutic strategies.