Abstract The oop RNA is a short (77 nucleotides (nt)) transcript encoded by bacteriophage λ which acts as an antisense RNA for λ cII gene expression. Recently we demonstrated that oop RNA is specifically polyadenylated at its 3′ end by poly(A) polymerase I (PAP I), the pcnB gene product. Here we demonstrate that the half life of oop RNA is 3 times longer in the pcnB mutant relative to the pcnB + host, indicating that polyadenylation of this transcript causes its accelerated degradation. Although it was proposed that polyadenylation of RNAs in bacteria leads to their enhanced degradation, in most cases stabilization of these molecules was observed only when other mutations ( pnp, rnb and rne) were present in the pcnB − strain. Therefore it seems that oop RNA may serve as a very useful model in further studies on molecular mechanisms of RNA polyadenylation and degradation in bacteria. Analysis of oop RNA and its degradation product isolated from Escherichia coli cells suggests that both polyadenylated and non-modified oop transcripts can act as antisense RNA.