Viruses are dependent on their host cells for replication. The first step in viral infection is the binding of the virus to the host cell membrane, followed by internalization or endocytosis of the virus. Rhinoviruses utilize several cellular membrane receptors to cross the plasma membrane by endocytosis. Three major glycoprotein receptors that are utilized by rhinoviruses to gain entry into the cells are intracellular adhesion molecules, low-density lipoprotein receptor family members, and cadherin-related family member-3. Rhinovirus is endocytosed by a clathrin- or dynamin-dependent mechanism. Upon uptake into an acidic endosomal environment, rhinovirus uncoats and injects its genome into the cytoplasm, where the viral replication begins. It is often difficult to differentiate between bound and the endocytosed rhinovirus in the cells. Here, we describe a method to quantify bound and endocytosed virus by flow cytometry.