It is well accepted that the 3 end of 16S rRNA is directly involved in prokaryotic translation initiation by pairing with the Shine-Dalgarno (SD) sequence, which is located in the ribosome-binding site of mRNA. According to Shine and Dalgarno, Escherichia coli s 5 UTR has the pattern of AGGAGG (SD sequence), which is complementary to the 3 end sequence of 16S rRNA. In this work, we systematically calculated free-energy values of the base pairing between the 3 end of 16S rRNA and the 5 UTR of mRNA, in order to analyze the base-pairing potentials in various prokaryotes. The free-energy values were then plotted over distances from the start codon to visualize the free-energy pattern of 5UTRs.