The present invention relates to Multicomponent Nucleic Acid Enzymes (MNAzymes) and methods for their use. MNAzymes comprise two or more oligonucleotide components which self-assemble in the presence of one or more MNAzyme assembly facilitator molecules to form a catalytically active structure. Compositions for making MNAzymes, and collections of MNAzymes are provided. Also provided are methods for using MNAzymes for the detection, identification and/or quantification of one or more targets. The methods can be practiced in solution-based assays or in assays where one or more reaction components are attached to a support structure. The methods allow for multiplexing the MNAzyme detection to detect multiple targets in a single reaction. Also provided are kits for making the compositions, and for practicing the methods provided herein.