More than 1,000 genomes of DNA phages have been identified in metagenomic datasets. By contrast, very little is known about RNA phages, with only 19 complete genome sequences available and only 2 families described: leviviruses (which have single-stranded RNA genomes) and cystoviruses (which have double-stranded RNA genomes). Wang and colleagues reasoned that genomes of RNA phages might be present in metatranscriptomic datasets and detectable by alignment methods. Indeed, such an approach enabled the assembly of partial genomes for 138 leviviruses and 5 cystoviruses, which represented an estimated 111 novel levivirus species and 3 novel cystovirus species. The expansion of the known diversity of RNA phages was further marked by the identification of novel host species and communities, including the first non-proteobacterium host (a Gram-positive bacterium) and microbial communities that inhabit invertebrates or sulfur springs.