Numerous virus families utilize endocytosis to infect host cells, mediating virus internalization as well as trafficking to the site of replication. Recent research has demonstrated that viruses employ the full endocytic capabilities of the cell. The endocytic pathways utilized include clathrin-mediated endocytosis, caveolae, macropinocytosis and novel non-clathrin, non-caveolae pathways. The tools to study endocytosis and, consequently, virus entry are becoming more effective and specific as the amount of information on endocytic component structure and function increases. The use of inhibitory drugs, although still quite common, often leads to non-specific disruptions in the cell. Molecular inhibitors in the form of dominant-negative proteins have surpassed the use of chemical inhibitors in terms of specificity to individual pathways. Dominant-negative molecules are derived from both structural proteins of endocytosis, such as dynamin and caveolin, and regulatory proteins, primarily small GTPases and kinases. This review focuses on the experimental approaches taken to examine virus entry and provides both classic examples and recent research on a variety of virus families.