The chest X-ray is the most commonly performed radiological examination in the intensive care unit. We used TLDs to measure the radiation exposure in 30 ICU patients due to portable chest radiography. The mean number of CXR was 3 (range 1-11). The mean surface entry dose at the xiphisternum was 1.8 mGy (range 0.43-5.14 mGy) per patient and 0.63 mGy per CXR. Very small amounts of radiation were detected at the symphysis pubis and in more than half of the patients no radiation was detected at this site. These values are well above accepted norms. Patient exposure may be reduced by ordering fewer X-rays or by changing to a faster screen-film combination.