A chimaeric poliovirus carrying a type-2-specific neutralization epitope on a type 1 capsid was created by site-directed mutagenesis of the Mahoney strain of poliovirus type 1. An EcoRV and a HindIII restriction sites were first constructed in the cDNA of poliovirus type 1 at nucleotide positions 2756 and 2786, respectively, i.e. on either side of the sequence encoding neutralization epitope C3 (VP1 amino acids 93-103), which is part of neutralization site NImI. The cDNA sequence framed by the two sites was next taken out and replaced by custom-made oligonucleotides encoding the equivalent region of VP1 from the Lansing strain of poliovirus type 2. The DNA from the plasmid carrying such a hybrid construct was transfected onto CV1 cells generating a chimaeric virus, v510. Neutralization of v510 with a panel of monoclonal antibodies showed that v510 has lost the poliovirus type 1 C3 epitope but acquired a new, poliovirus type-2-specific neutralization epitope. Preliminary results indicate that v510 also shows neurovirulence for mice, which is a specific trait of the Lansing strain of poliovirus type 2.