A method for the in vitro amplification of a nucleic acid in a sample, said nucleic acid being from one or more species in the class Mollicutes, comprising the steps of: (a.) contacting a sample with at least two tagged amplification oligomers, each of which individually comprises a target hybridizing region and a tag region, wherein a first of said at least two tagged amplification oligomers comprises a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 4752 to 4798 of SEQ ID NO:2, and a second of said at least two tagged amplification oligomers is selected from the group consisting of: (i) a tagged amplification oligomer comprising a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 1954 to 2006 of SEQ ID NO:3; and (ii) a tagged amplification oligomer comprising a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 1994 to 2036 of SEQ ID NO:4; and (b.) providing suitable conditions for performing an in vitro amplification reaction. (a.) contacting a sample with at least two tagged amplification oligomers, each of which individually comprises a target hybridizing region and a tag region, wherein a first of said at least two tagged amplification oligomers comprises a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 4752 to 4798 of SEQ ID NO:2, and a second of said at least two tagged amplification oligomers is selected from the group consisting of: (i) a tagged amplification oligomer comprising a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 1954 to 2006 of SEQ ID NO:3; and (ii) a tagged amplification oligomer comprising a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 1994 to 2036 of SEQ ID NO:4; and (i) a tagged amplification oligomer comprising a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 1954 to 2006 of SEQ ID NO:3; and (ii) a tagged amplification oligomer comprising a target hybridizing region that is from 15 to 50 nucleobases in length and contains a nucleotide sequence that is configured to specifically hybridize to all or a portion of a region of a target nucleic acid corresponding to residues 1994 to 2036 of SEQ ID NO:4; and (b.) providing suitable conditions for performing an in vitro amplification reaction.