The infrared spectral characteristics of N-(2-hydroxybenzylidene)aniline, its deuterium substituted analogue, N-(2-hydroxybenzylidene)-m-toluidine, and their photoproducts have been investigated. The infrared spectrum of a low temperature polycrystalline film of N-(2-hydroxybenzylidene)aniline exhibits new absorption bands at 3380, 1646, 1537, 1502, 1319, and 1310 cm−1 upon irradiation at 365 nm. Likewise, the spectrum of the m-toluidine derivative exhibits new absorption bands at 3320, 1650, 1535, 1503, 1321, 1310, and 995 cm−1 upon irradiation at 365 nm. These new data, in conjunction with the newly acquired data on the hydrochloride and deuterochloride of the title compound, indicate that the photoproduct is a zwitterion, not an ortho-quinone. It is also inferrred that the photoproduct exists in a conformation which is cis about the central carbon–nitrogen double bond.