The stopping cross sections of Li, Cu, LiF, Ca${\mathrm{F}}_2$, Pb, and Au for protons have been measured over the energy range $E_p=50-600\mathrm{}$ kev; the stopping cross section of Be for protons has been measured for $E_p=50-2600\mathrm{}$ kev. An electrostatic analyzer and magnetic spectrometer were used to measure the energy loss of protons in a thin film of the stopping material. The density of the stopping film was determined by weighing, or by quantitative chemical analysis of, a known area. The ratio of the stopping cross section of Al, Cu, Mn, Ta, and Pb to that of Au was measured by observing the yield of elastically scattered protons from these targets for $E_p=200-600\mathrm{}$ kev. The ratio of stopping cross section of Ca, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, to that of Mn was measured for $E_p=200-600\mathrm{}$ kev by the same method. In the region $Z=23-29\mathrm{}$, the stopping cross section decreases as the atomic number of the stopping material increases. The probable error of absolute stopping cross section measurements in this experiment is 3%.

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