Rate constants have been determined for the quenching of NH(a(1) Delta,v=0) by a number of molecular halogens and interhalogens. The values measured are (1.0 +/- 0.5) x 10(-13), (3.7 +/- 0.4) x 10(-11), (6.8 +/- 0.4) x 10(-11) (6.0 +/- 0.3) x 10(-11), and (1.6 +/- 0.3) x 10(-10) cm(3) s- for quenching by F-2, CIF, Cl-2, Br-2, and ICl, respectively. For quenching by ClF, Cl-2, and Br-2, excited singlet halogen nitrenes and vibrationally excited hydrogen halides were detected as products of the quenching processes. This result is interpreted as indicating NH(a(1) Delta) insertion into these molecules. For NH(a(1) Delta) quenching by ClF, production of NF(a(1) Delta) predominates over production of NCl(a(1) Delta).