Bacteria secrete RNAs, some of which have effects on other cells and on other species as signalling RNAs. Prokaryotic membrane vesicles (MVs) contain a range of RNA types. The MV structure offers protection from degradation as well as receptors to facilitate delivery to target cells. Microscopic imaging and molecular biology analyses have provided evidence to demonstrate that bacterial MVs deliver their RNA into eukaryotic cells. Moreover, in some cases the RNA cargo is demonstrably functional and phenotypic changes can be identified in MV-RNA treated target cells. The challenge now is to dissect the effect of MV-RNA on target cells away from the effects of non-RNA components of the MV such as lipopolysaccharide that can co-purify with RNA.