By combining the selectivity of high-resolution laser spectroscopywith the specificity of hyperfineinteractions in zero-field magnetic-resonance spectroscopy,13C-containing isotopomers of pentacene havebeenobserved in natural-abundance samples and 1H-containingisotopomers of pentacene in "fully" deuteratedsamples. Molecules containing two 13C nuclei or up tofour residual 1H nuclei have been identified.