An experimental program was conducted to investigate the properties of the unresolved rotational fine structure of the NO &ggr;00band. The experimental values were taken spectroscopically in absorption at controlled temperatures.An analytic expression representing the unresolved fine structure is utilized to compute absorption coefficients and absorption intensities for the experimental temperatures. A doublet model and a singlet model of the band are investigated.From the experimental absorption coefficients, temperatures are determined to within 6% of the directly measured values. The rotational constants of the upper and lower states are determined to accuracies of 13 and 6%, respectively, of the known values.