Intermolecular complementary base pairs, that can be formed between the bases from single-stranded and weak stem regions on 16S rRNA and those on 23S rRNA, were located and checked for preservation in a variety of species covering the complete phylogenetic spectrum. Putative base pairs that exhibited two 'compensatory base pair changes' (a requisite as dictated by the approach of 'comparative sequence data analysis') were picked up. Potential base pairs were selected by assessing the frequency and taxonomy specificity of the occurrence of compensatory base pair changes against those of other types of base pair changes. The selected base pairs were classified as universal, non-mitochondrial, and prokaryote-specific. The positions of the proposed base pairs occur near the structurally and functionally important regions on rRNAs.