Two small nuclear RNA species (U6 RNA and a 4.5S,-like RNA) not described so far for plants were detected in broad bean (Vicia faba L.) nuclei. U6 RNA is 98 nucleotides long, contains ¥ and methylated nucleotides and shows a surprisingly high degree of sequence homology (80%) with its rat counterpart, particularly in the middle part (a 57 nucleotide-1ong stretch) of the molecule, where it amounts to 98%. The 4.5S,-like RNA, similar in its structure to 4.5Sr RNA detected so far only in rodent nuclei, is 94 nucleotides long, contains f and an unidentified nucleotide and exhibits 52% overall sequence homology with rat 4.5S. RNA. A block of 20 consecutive nucleotides at the 5' end of the molecule is conserved between broad bean 4.5Sj-like RNA and rat 4.5S, RNA. The presence of the two RNA polymerase III internal promoter consensus sequences in 4.5Sj-like RNA suggests that it is an RNA polymerase III transcript.