Exosome complex is widely conserved, functionally versatile, and essential constituent of the machinery regulating gene expression in the nucleus as well as in the cytoplasm. While the most fundamental enzymatic property of exosome is ribonucleolytic activity, its in vivo functions are varied, highly specific, and tightly regulated, and include RNA degradation, processing, and quality control. Recent reports reveal that exosome also has a prominent role in gene silencing as well as in regulating the expression of a wide variety of noncoding RNAs. Taken together with the emerging notion of pervasive genomewide transcription, these findings indicate that 'policing the transcriptome' may well turn out to be the major role of exosome in eukaryotes.