Electron nuclear double resonance (ENDOR), electron nuclear nuclear (TRIPLE) resonance and electron spin echo envelope modulation (ESEEM) experiments permit a considerable enhancement in resolution relative to electron paramagnetic resonance for the determination of small hyperfine interactions. Such measurements applied to various polyacetylene samples permit determination of the wavefunction of the S = 1 2 defect (e.g., the soliton wavefunction). Experimental results are discussed in terms of various theoretical calculations. Special attention is given to discussing the limitations of both experimental and theoretical results. © 1984.