Bacteriophage phi 6 has a genome of three segments of double-stranded RNA enclosed in a procapsid composed of four different proteins. The preformed procapsid is capable of packaging plus-strand transcripts of the genomic segments in an in vitro reaction. The packaging-specific sequences on the RNA molecules are located near the 5' ends. In this study we show that the packaging sequences are different for each of the three segments and that they are of about 250 nucleotides in length. Although these sequences are consistent with some secondary structure, there is no clear structural similarity between the packaging regions of the three segments.