The nuclear spectra of ${\mathrm{Sb}}^{125}$, ${\mathrm{Te}}^{125*}$, ${\mathrm{Cr}}^{51}$, and ${\mathrm{I}}^{131}$ have been measured with a magnetic lens spectrometer. ${\mathrm{Sb}}^{125}$ has a beta-ray end point at 0.621 Mev, a lower energy group at 0.288 Mev, and perhaps some groups of still lower energy. The gamma-rays of ${\mathrm{Sb}}^{125}$ are at 0.125 (I.C.), 0.174 (I.C.), 0.431 (I.C.), 0.466, 0.609 (I.C.), and 0.646 Mev. Those marked with the notation (I.C.) are internally converted. The metastable state of ${\mathrm{Te}}^{125}$, daughter of ${\mathrm{Sb}}^{125}$, is characterized by the emission of an internally converted gamma-ray of energy 0.110 Mev. ${\mathrm{Cr}}^{51}$ emits no positrons but decays by $K$-capture accompanied by two gamma-rays of energies 0.323 and 0.267 Mev, the latter being entirely internally converted. ${\mathrm{I}}^{131}$ has a beta-ray end point of 0.605 Mev with a lower energy group at 0.250 Mev. Gamma-rays at 0.080, 0.282, 0.363, and 0.637 Mev are observed. The disintegration schemes of ${\mathrm{Sb}}^{125}$, ${\mathrm{Te}}^{125*}$, and ${\mathrm{I}}^{131}$ are discussed.

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