Eleven microwave transitions in the frequency range from 10.5 to 11.5 GHz have been observed between excited electronic states of CN. These correspond to 11 of 13 allowed magnetic-dipole transitions, $\Delta F=0,\pm 1$, in the $K^{\prime }=4\mathrm{}$ perturbation complex between the three hyperfine levels of the perturbed component of the $\Lambda$ doublet of the $A^2{{\Pi }_{\frac{3}{2}}}^{+} \mathrm{}(v=10\mathrm{})\mathrm{}$ level and the three hyperfine levels in each of the perturbed and the unperturbed components of the spin doublet of the $B^2{\Sigma }^{+} \mathrm{}(v=0\mathrm{})\mathrm{}$ level. These transitions and the previously measured 13 electric-dipole transitions determine all 12 hyperfine energy levels of this perturbation complex. The experiment is the first microwave measurement of magnetic-dipole transitions between excited electronic states of a molecule. CN was produced predominately in the metastable $A^2\Pi$ state by a chemical reaction when methylene chloride was added to a nitrogen afterglow. Resonant microwave pumping from the II state increased the population of the three hyperfine levels of each $\Sigma$ state. The population change was detected by measuring an increase in the intensity of the $B^2{\Sigma }^{+}\to X^2{\Sigma }^{+} \mathrm{}(0,0)\mathrm{}$ violet band of CN near 3875 Å.

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