Several cellular responses are regulated at the translational level, particularly by selective translation of specific mRNAs or by inhibition of the ribosome and protein synthesis, as these processes consume a large amount of energy. Such inhibition can follow various stimuli, including endoplasmic reticulum stress and unfolded protein response (UPR), transition into quiescence and different stress-related and cell death-related signals (66). The most straightforward and fastest way to achieve translation inhibition is to target ribosomal RNA. Interestingly, it has been proposed that repression of protein synthesis during UPR in human cells is due to the cleavage of 28S rRNA by hIRE1b, a second homologue of IRE1 (67) . Also, during apoptosis in some mammalian cells degradation of 28S rRNA by RNaseL, but also of other RNAs such as Y RNA or some mRNAs, has been suggested to block protein synthesis that contributes to, but could even initiate, cell death. Furthermore, damage to the 28S rRNA may act as a ribotoxic stress and induce an early death-committing signal through activation of SAP and MAP kinases (68, 69) . These possibilities were not examined in yeast PCD pathways. We have analysed the behaviour of ribosomal RNAs during oxidative stress and in apoptotic pathways that are induced by different stimuli. We have observed that cells exposed to all apoptotic conditions tested, such as H 2 O 2 , acetic acid, hyperosmotic stress (60% glucose) and ageing, reveal a significant degradation of the 25S and some of 5.8S rRNAs, with a much lesser effect on the 18S rRNA. The decay of mature rRNAs was accompanied by the accumulation of treatment-specific, yet partly overlapping degradation intermediates.