The present invention concerns a method for detecting the presence of a catalytically active ribozyme in a medium. The detection of the catalytically active ribozyme may be a goal by itself, or the ribozyme may serve as a reporter for the presence of other biomolecules in an assayed sample. The detection is carried out in a catalytic system wherein the presence of the active ribozyme serves to produce other active ribozyme in a positive-feedback amplificatory manner.