[en] Radiofrequency (RF) fields of various intensities are increasingly present in our environment. The sources of these RF signals are numerous. No previous work that evaluates ionizing radiation detection instrument performance in RF fields has been reported. The purpose of this limited study was to investigate the effects, if any, of RF fields on x-ray measurement devices. The results of this study show that when ionizing radiation measurements must be made in areas where RF fields can be expected to occur (i.e., hospitals, airports, and so forth), extreme care in the use of ionization chamber type instruments must be exercised. Presently, BRH is investigating methods of RF shielding modifications of existing x-ray detection/measurement equipment