Plant genes usually have multiple potential poly(A) addition signals, and different sites are used for 3' processing of transcripts from a single gene. In contrast, we show here that four barley genes that also have multiple poly(A) addition signals conforming to the plant consensus use only one signal. In each of these genes, the region of cleavage for poly(A) addition is centered on a conserved pentanucleotide. This AGGCA is followed by a conserved sequence homologous to sequences involved in self-cleavage of plant viroid RNA precursors; immediately following, in turn, are four or five nucleotides complementary to the nucleotides immediately preceding AGGCA in each gene. The presence of these conserved sequences and their association with a single region for poly(A) addition in three different gene types (high-pI and low-pI alpha-amylase genes and a thiol protease) that otherwise are not homologous in their 3' untranslated/flanking sequences suggest that they might participate in some common regulatory mechanism shared by these genes.