The Herman-Kaplan system of N 2 has been observed for the first time under high resolution and rotational analyses of four bands have been carried out. It is shown that the upper state, E, is of species of 3Σg+ with a rotational constant B0, of 1.927 3 cm -1 and a T0 value of 95 774.50 cm -1. No spin splitting is detected in the E state within the limits of experimental error. The results establish that the state is, as proposed by Mulliken, the 3Σg+ state obtained by the addition of a 3 sσg Rydberg electron to the X 2Σg+ ground state of N 2+. The data for the lower state are in good agreement with those which have been derived from studies of the first positive system.