A minizyme is a hammerhead ribozyme with short oligonucleotide linkers instead of stem/loop II, In a previous study we demonstrated that a minizyme with high-level activity forms a dimeric structure with a common stem II (Amontov and Taira, J, Am. Chem, Sec., 118 (1996) 1624-1628), As a continuation of this study, we recently examined whether a short oligonucleotide linker at stem/loop II could be replaced by a triterpenoid linker and whether the resulting minizymes with bulky hydrophobic groups would form dimeric structures, In contrast to the minizyme with high-level activity that we characterized in the previous study, minizymes that contained a triterpenoid group had low cleavage activities, The nature of the dependence of the activity on the concentration of ribozyme revealed that these minizymes with a triterpenoid group do not form dimeric structures, Thus, the low activities of these structures ran be attributed to their failure to form dimers.