RNAdb contains more than 500 mammalian snoRNAs and scaRNAs. The snoRNAs fall into two general classes, C/D box and H/ACA snoRNAs, which classically guide ribose methylation and pseudo-uridylation of rRNAs respectively. Interestingly, some snoRNAs appear to regulate other RNAs.  Human snoRNAs and scaRNAs in RNAdb were derived from snoRNA-LBME-db (release 3, August 2006) (Lestrade and Weber, 2006), and annotations for these sequences are maintained by linking out to this informative and specialized resource.