A method for the selective amplification of a target nucleic acid in a mixture of nucleic acids comprising target nucleic acid and one or both of non-target nucleic acid and contaminating nucleic acids, said method comprising the steps of: a. selectively hybridizing and capturing a target nucleic acid from a nucleic acid sample using an inactivatable target capture oligomer comprising a target hybridizing region that is at least 15 nucleobases in length, joined on either its 5' end or its 3' end by a binding pair member, and joined on the other of its 3' end or 5' end by a tag closing region that is at least 3 nucleobases in length; wherein capturing the target nucleic acid from the sample comprises the steps of: (i) treating the sample with the inactivatable target capture oligomer; (ii) providing a set of conditions wherein the stringency of the conditions biases the target hybridizing region of the inactivatable target capture oligomer towards stably hybridizing with the target nucleic acid and not towards stably hybridizing with its tag closing region; (iii) providing a change in the set of conditions in step a(ii) wherein the stringency is reduced, thereby allowing any inactivatable target capture oligomer that is not stably hybridized with target nucleic acid to form an inactive configuration by hybridizing its tag closing region with its target hybridizing region; and (iv) performing a capture step wherein a complex comprising the inactivatable target capture oligomer hybridized to target nucleic acid is captured; b. performing an amplification reaction to generate from a target nucleic acid captured in step a(iv) an amplification product; and c. detecting the amplification product to determine the presence or absence of the target nucleic acid. a. selectively hybridizing and capturing a target nucleic acid from a nucleic acid sample using an inactivatable target capture oligomer comprising a target hybridizing region that is at least 15 nucleobases in length, joined on either its 5' end or its 3' end by a binding pair member, and joined on the other of its 3' end or 5' end by a tag closing region that is at least 3 nucleobases in length; wherein capturing the target nucleic acid from the sample comprises the steps of: (i) treating the sample with the inactivatable target capture oligomer; (ii) providing a set of conditions wherein the stringency of the conditions biases the target hybridizing region of the inactivatable target capture oligomer towards stably hybridizing with the target nucleic acid and not towards stably hybridizing with its tag closing region; (iii) providing a change in the set of conditions in step a(ii) wherein the stringency is reduced, thereby allowing any inactivatable target capture oligomer that is not stably hybridized with target nucleic acid to form an inactive configuration by hybridizing its tag closing region with its target hybridizing region; and (iv) performing a capture step wherein a complex comprising the inactivatable target capture oligomer hybridized to target nucleic acid is captured; (i) treating the sample with the inactivatable target capture oligomer; (ii) providing a set of conditions wherein the stringency of the conditions biases the target hybridizing region of the inactivatable target capture oligomer towards stably hybridizing with the target nucleic acid and not towards stably hybridizing with its tag closing region; (iii) providing a change in the set of conditions in step a(ii) wherein the stringency is reduced, thereby allowing any inactivatable target capture oligomer that is not stably hybridized with target nucleic acid to form an inactive configuration by hybridizing its tag closing region with its target hybridizing region; and (iv) performing a capture step wherein a complex comprising the inactivatable target capture oligomer hybridized to target nucleic acid is captured; b. performing an amplification reaction to generate from a target nucleic acid captured in step a(iv) an amplification product; and c. detecting the amplification product to determine the presence or absence of the target nucleic acid.