The results of experimental studies of generation of supershort avalanche electron beams (SAEBs) in gas-filled diodes and the analysis of the techniques for measurements of their amplitude-time characteristics are presented. The optimal conditions for obtaining the maximum SAEB amplitudes are described. It is shown that, at a 6-mm-diameter cathode and a 10-mm interelectrode distance, a beam is detected over the entire foil area, the diameter of which is 50 mm, and equals the inner diameter of the gas diode. A half-height duration of the beam-current pulse shorter than 90 ps was measured with the use of a collector with a 3-mm-diameter receiving element. The SAEB amplitude measured behind the 10-μm-thick Al foil at this pulse duration was ∼50 A.