The potential consequences of the reintroduction of poliovirus in the post-eradication era range from trivial (no or self-limited transmission and no clinical cases) to very serious (return of continued transmission of polioviruses and abandonment of the poliomyelitis eradication goal). This paper summarises the key determinants of such outcomes and identifies factors relating to infection surveillance, to vaccination policies at the time of OPV cessation and beyond, and to the still-unknown implications of these policies for infection transmission in environments with poor sanitation, as particularly important. Explicit consideration of these issues should encourage studies on the effectiveness of IPV vaccines in reducing poliovirus transmission in tropical environments, and should influence the location and containment requirements of facilities for vaccine production and storage, and for poliovirus-related research, in the era after cessation of OPV.