Experimental results presented here demonstrate that the poliovirus empty capsid binds with saturable character to poliovirus-susceptible cells, binds preferentially to susceptible cells, and competes with mature virus for binding sites on cells. Hence, induced changes in the structure and/or stability of the particle by RNA encapsidation and virus maturation are not necessary for recognition by receptor. In mature virus, heat-induced rearrangements mimic those induced by receptor at physiological temperatures in several important respects, namely, expulsion of VP4 and externalization of the VP1 N-terminal arm. It is shown here that in the empty capsid the VP1 N-terminal arm is externalized but the VP4 portion of VP0 is not. Thus, these two hallmark rearrangements associated with cell entry can be uncoupled.