The precise role of the poly(A) tail at the 3'-end of the calicivirus RNA genome is unknown. To study the relationship between the presence of the poly(A) tail and the infectivity and replication of rabbit hemorrhagic disease virus (RHDV), mutants of an infectious cDNA clone of RHDV were constructed, and RK13 cells were transfected with transcripts from these mutants. Transcripts with and without a poly(A) had a fairly similar ability to infect and replicate, suggesting that a long 3'-terminal poly(A) is not essential for infectivity and replication. RT-PCR with specific primers, using viral RNA recovered from RK13 cells transfected with poly(A)-deficient RNA transcripts, showed that the poly(A) tail was restored in vivo.