The effect of temperature on the disproportionation equilibrium of the radical anion of N-diphenylmethyleneaniline in tetrahydrofuran has been examined by determining the radical anion concentration at different temperatures by electron spin resonance. The following values were obtained for the disproportionation reaction: ΔG° at 0°= 3·35 kcal. mole^–1; ΔH°=–12·8 kcal. mole^–1; ΔS° at 0°=–59·2 cal. mole^–1 deg.^–1. The action of light (λ= 3660 Å) on the di-anion converts it into the radical anion. Further action of light (λ= 3130 Å) destroys the radical anion.