The reactivity of a sigma,sigma,pi-triradical, N-methylene-5,8-didehydroisoquinolinium ion, has been compared to that of four related mono- and biradicals in a Fourier transform ion cyclotron resonance mass spectrometer. The triradical contains two weakly interacting orthogonal radical systems-the sigma,sigma-biradical moiety and the pi-monoradical moiety. The sigma,sigma-biradical moiety is found to be substantially more reactive than the pi-radical moiety. The pi-radical site reacts only after reactions have quenched the sigma-radical sites.