A detailed analysis has been made of the vibrational constants for the ground state of OH, combining the observations of the night-sky rotation-vibration bands with laboratory data for the ultraviolet electronic OH bands. Systematic deviations were observed from the band positions predicted by w and c X from the ultraviolet bands. The deviations show, however, that the assignment of terms in w,y , w , would not have any physical significance. The relative intensities have been determined for the night-sky bands from 9000 to 5500 A. The resultant values show systematic changes of band intensity within each Av sequence. A brief investigation of tbe band intensities under conditions of radiative equilibrium for cases of resonance and thermal excitation shows that the OH bands are probably produced by a chemical resonance mechanism and, further, that collisional de-excitation effects may be present. The temperature in the OH stratum was found to be 260 + 5 K from the distribution of energy in the resolved P branches and from the ratio of intensity between the P, Q, and R branches.