N-Nitrosodialkylamines underwent photolysis in the presence of an acid. From the analysis of the end products, the primary photolysis products were shown to be [NOH] and the corresponding alkylideneimine, which underwent further reaction, e.g. (i) recombination of the two species to give amidoximes, (ii) hyponitrous acid formation, and (iii) hydrolysis or polymerization. A pathway is proposed for the reaction. Evidence is presented to show that the formation of the parent amines was not the result of hydrolysis of nitrosamines.