Abstract. A comparison of two standard humidity generators (two-temperature (2-T) and one-temperature (1-T) generators) that are developed by the National Institute for Standards (NIS) has been performed using a transfer standard chilled-mirror hygrometer and measurement procedures to realize dew-point temperature T d in the range from À50°C to 0°C. The main objective of this comparison was to compare the realizations of dew-point temperature and to establish the level of consistency between the two generators. For a level of consistency between two measurements, it is expressed by the difference between the measured values, m 1 À m 2 , and the expanded pair uncertainty of this difference U p [1]. The comparison measurements revealed dew-point temperature differences of 0.02°C and 0.07°C with expanded pair uncertainties of ±0.09°C and ±0.15°C.