The focusing and other properties exhibited by gas-focused and electron-lens-focused oscillographs when radio frequencies and ultra-high frequencies of deflection are used, are compared and contrasted. The superior focusing properties of, and absence of origin distortion in, the electron-lens-focused tube are demonstrated.Characteristics peculier to either tpe of tube are discussed, and some phenomene common to both types, when used at very high frequencies, are discribed.Finally, two applications of the cathode-ray oscillograph at very high frequencies are suggested.