The authors designed a hammerhead ribozyme, mRibSAA2, to cleave the mRNA for mouse acute phase serum amyloid A 2 (A-SAA2), a major acute phase protein that is massively induced during inflammation and that is deposited as fibrils during secondary amyloidosis. Using computer based secondary structure analysis, a GUC triplet (nucleotides 408-410) on a predicted stem loop in A-SAA2 mRNA was chosen as the target site for mRibSAA2. The ribozyme was tested in vitro and gave efficient and specific magnesium-dependent cleavage of mouse A-SAA2 mRNA into the expected fragments of 197 and 425 bases. The authors also demonstrated that the ribozyme retains cleavage activity over several hours. The use of the mRibSAA2 ribozyme as a research tool and possible therapeutic agent in mouse models of amyloidosis is discussed.