RNA 2 of the V strain of tomato aspermy virus (TAV) consists of 3074 nucleotides and contains one open reading frame of 2487 nucleotides. Thus, it resembles RNA 2 of cucumber mosaic virus (CMV) strains Q and Fny (62% identical to both), brome mosaic virus (42% identical) and cowpea chlorotic mottle virus (40% identical). In comparisons between amino acid sequences, three different regions of similarity could be distinguished. These were the central part (amino acids 224 to 757 for V-TAV), which was most similar among the four viruses, and the N and C ends; sequences conserved among RNA polymerase species were found in the C half of the central part. Hydrophobicity patterns, and distributions of acidic and basic amino acids in the proteins encoded by V-TAV RNA 2, Q-CMV RNA 2 and Fny-CMV RNA 2 were very similar except at the extreme ends of the molecules. Structures that have been reported to act as regulatory signals for minus- and plus-strand synthesis were found in the 5' and 3' non-coding regions of the RNA.