Small non-messenger RNAs (snmRNA) do not encode proteins but perform distinct cellular functions. In the June 1 EMBO Journal, Huttenhofer et al. describe an experimental approach to discover novel snmRNAs (EMBO Journal 2001, 20:2943-2953). Their approach involves the random sequencing of small RNA species to generate 'expressed RNA sequences' (ERNS), similar to the EST-based characterization of mRNA. Huttenhofer et al. constructed cDNA libraries of small RNAs (50-500 nucleotides) from mouse brains. Screening with known snmRNA sequences enriched for novel RNA species. They identified 201 novel ERNS, which they assigned to 13 different subgroups. Over half of the sequences correspond to new members of the two subclasses of small nucleolar RNA (snoRNAs) that guide RNA ribose methylation. Some of these may direct modification of spliceosomal small nuclear RNA (snRNA), while many have unidentified RNA targets. They also provide evidence for the expression of brain-specific snoRNA species.