Uridine addition at the 3' end of RNAs (i.e., uridylation) emerges as a critical posttranscriptional modification promoting RNA degradation. Uridylation has been notably linked to the degradation of small RNAs, correlated with the 5' shortening of RISC-cleaved transcripts and the degradation of mRNAs. We describe here a method based on 3' RACE (3' Rapid Amplification of cDNA End) PCR that has been successfully used to investigate nucleotide addition at the 3' end of RISC-cleaved transcripts and full-length mRNAs in plants.