Photolysis of N-tert-butyl-3-methylanthranilium ion as well as its 5-halo and methyl derivatives produces transient nitrenium ions via an electrocyclic ring-opening process. This is confirmed by identification of the stable products and transient absorption experiments. Laser flash photolysis of the substituted anthranilium ions gives short-lived (80-200 ns) species which absorb in the UV and visible region of the spectrum. These transient species react with nucleophiles such as alcohols and water with rate constants ranging from 10(6)-10(9) M(-1) s(-1). Reactivity of the nucleophiles follows the trend MeOH > EtOH > i-PrOH similar to H2O > t-BuOH. This is the same trend that has been observed by others for diarylcarbenium ions and styrene cation radical cations and provides further confirmation for the assignment of the spectra to the singlet state arylnitrenium ions.