Intrinsic carrier concentrations of narrow-gap Hg1-xCdxTe alloys (0.17≦ x ≦0.30) have been calculated as a function of temperature between 0 and 300 K by using the new nonlinear temperature dependence of the energy gap obtained previously by twophoton magneto-absorption measurements for samples with 0.24≦ x ≦0.26. We report here experimental values for Eg (x,T) for samples with x = 0.20 and 0.23 obtained by one-photon magneto-absorption measurements. These data confirm the validity of the new Eg (x,T) relationship for these : values. In this range of composition and temperature, the energy gap of mercury cadmium telluride is small, and very accurate values are needed for the gap to obtain reliable values for the intrinsic carrier density. Large percentage differences exist between our new calculations and previous values for ni at low temperatures. Even at 77 K, differences approaching 10 percent exist, confirming the importance of using the new ni results for materials and device characterization and a proper understanding of device operation in long-wavelength materials.