The principles and practice of nitrosamine degradation by photochemical means were described. Two types of apparatus were constructed for this purpose. A nitrosamine waste solution containing 10-3-10-1 N in hydrochloric acid and about 10 mole-equivalents of an HNO2 scavenger (i.e., urea, guanidine, or hydrazoic acid) was efficiently and irreversibly degraded to the parent amines and N2 (and/or N2O) by irradiation. Efficiency of the degradation depended on the type of apparatus used. With the use of one apparatus, about 11 g N-nitrosodimethylamine was photolytically converted to dimethylamine, N2, and N2O in 24 hours. Protonated guanidine catalyzed the photohydrolysis processes.