The infrared absorption and Raman spectra, evaluation of potential energy constants with various potential functions, and other spectroscopic studies have been briefly analyzed for the isotopic species of nitrogen trichloride molecule possessing a trigonal pyramidal symmetry. Among the various quantum mechanical models, the delta-function potential model based on the variational method and the delta-function electronic wave functions has been employed here to evaluate the atomic polarizabilities, the contributions by the bonding and nonbonding electrons to the bond parallel component of the polarizability, the bond perpendicular component of the polarizability, and the mean molecular polarizability of nitrogen trichloride. On the basis of group theoretical considerations, the symmetrized mean- square amplitudes, mean-square amplitudes, and root-meansqare amplitudes for both bonded and nonbonded atom pairs have been computed at the temperatures 298 °K and 500°K. On the basis of a rigid rotator and harmonic oscillator approximation, enthalpy function, free enthalpy function, entropy, and heat capacity have been computed for the temperatures from 200°K to 2000° K for both isotopic species of nitrogen trichloride. A discussion of the results follows.