A survey of the possibilities of determining the ionization losses caused by ion recombination in thimble chambers irradiated with roentgen rays of very high intensity is presented. Dose measurements were made, and saturation curves are shown illustrating the performance of 2 common types of chambers irradiated with short roentgen pulses from the discharge tube earlier described by Sievert. It is possible to deliver with this tube, in a small volume, roentgen doses up to 1000 r with dose-rates up to 107 r/second, the pulse duration being shorter than 100[mu]s. It is shown that even at. these high dose-rates, the saturation in the chambers can easily be determined by help of the common formulae used at moderate dose-rates. A method is suggested for calculating the real dose when the dose-rate is not known sufficiently well to permit a direct estimation of the correction that should be applied to the measured values because of the ion recombination.