Bromoviruses are a group of spherical plant RNA viruses. Their genome consists of approximately 8, 000 nucleotides in total and contains only four genes: 1a and 2a genes necessary for viral RNA replication, 3a gene required for viral cell-to-cell movement and the coat protein gene. Bromoviruses produce a large number of progeny virus particles in host plants, but never induce death. Therefore, we suppose that these viruses are adapted to host plant cells in various ways. Here, I describe molecular mechanisms of bromovirus adaptation to host plant cells and non-host plants.