Since 1993, NWS has been reporting radiosonde rlative humidity for values belowe 20% and at temperatures below -40°C. Before this time, relative humidity measurements taken in these conditions were reported as missing or were assigned a fixed value. The NWS is assessing the accuracy of radiosonde relative humidity sensors with emphasis on their performance in low relative humidity and cold environments. This is being done through analysis of sounding data and sensor tests conducted in environmental chambers. The intent of this paper is to provide some of the results of the analyses conducted to date