The photochemical reactions of resist films consisting of poly(methyl methacrylate) (PMMA) and aromatic azide at high concentraton (25 wt.%) were studied. Both p-azidobenzoic acid (PABA) and 2,6-bis(4-azidylbenzylidene)-4-methyl cyclohexanone(2,6-bisazide) were used as the azide compounds. Chemical analysis carried out on the photoproducts of deep-UV irradiated PMMA-azide films revealed them to consist of unreacted azide compound, primary amine, azo dye, and PMMA with pendant secondary amines formed by nitrene insertion reactions. It is concluded that formation of secondary amines resulting from nitrene insertion to the PMMA chain were mainly responsible for both the dissolution rate retardation and the image reversal observed in the exposed PMMA-azide resist.