The electromagnetic environment in a hospital is characterized in order to evaluate the conditions for failsafe operation of critical electronic equipment. Field strengths within the University Hospital Z¨urich were measured at more than 60 different locations in the frequency range from 9 kHz up to 10 GHz. To account for variations in both, time and location, 'stationary short term' and 'stationary long term' measurements over 24 h were carried out. The measurement uncertainty of the measurement equipment, calibration and measurement procedure is assessed. Measurement results are evaluated with respect to given immunity levels (EMC) and in-band interferences (EMI). The ISM band features a noise power density of -32 dBm/MHz while for Ultra Wide Band (UWB) there are different sub-bands with a maximum noise power density of less than -81 dBm/MHz. This suggests that communication in the UWB band requires significantly lower power levels than communication in the ISM band for equal dynamic ranges of the radio links. Abstract-The electromagnetic environment in a hospital is characterized in order to evaluate the conditions for failsafe operation of critical electronic equipment. Field strengths within the University Hospital Zürich were measured at more than 60 different locations in the frequency range from 9 kHz up to 10 GHz. To account for variations in both, time and location, 'stationary short term' and 'stationary long term' measurements over 24 h were carried out. The measurement uncertainty of the measurement equipment, calibration and measurement procedure is assessed. Measurement results are evaluated with respect to given immunity levels (EMC) and in-band interferences (EMI). The ISM band features a noise power density of -32 dBm/MHz while for Ultra Wide Band (UWB) there are different sub-bands with a maximum noise power density of less than -81 dBm/MHz. This suggests that communication in the UWB band requires significantly lower power levels than communication in the ISM band for equal dynamic ranges of the radio links.