The photochemistry of N- alkylphthalimides has been extensively studied while to date no work has been published on N-acylphthtalimidea. We were interested in the photochemical reactions of a range of N-acylphthalimides with toluene and cyclohexene. N-flcetylphthalimide. N-acetyl-3,4.5.6-tetrachlorophthalimide and N-benzoyl-3,4,5.6-tetrachlorophthalimide were found to behave photochemically like the carbonyl group of simple ketone systems by undergoing what appeared to be hydrogen abstraction at the "in-ring" carbonyl group of the excited phthalimide and recombination with the resultant benzyl radical to yeild the respective carbinols as the major products. N-Benzoylphthalimide when irradiated in toluene produced a novel spirolactone as the major product. We proposed the mechanism for its formation as involving a pinacol intermediate. The spirolactone formation may involve electron transfer from toluene to the excited N-J?enzoy lphthal imide whereas hydrogen abstraction may be the primary photoprocess on irradiation of the other studied N-acylphthalimides. Irradiation of N-benzoylphthalimide, N-acetylphthalimide and N-acety1-3,4,5,6-tetrachlorophthalimide ln the presence of cyclohexene resulted in 1,4-cycloaddition of the cyclohexene to the aromatic ring of the phthalimide as the major photoprocess. X-Ray crystallography showed the 1.4-cycloadduct from the irradiation of N-benzoylphthalimide in the presence of cyclohexene as the exo, trans 1,4-cycloadduct. The exo. trans 1.4-cycloadducts were also the major products on irradiation of N—acetylphthalimide and N-acety1-3,4,5. 6- tetrachlorophthalimide in the presence of cyclohexene. Minor products obtained on irradiation of N-acylphthalimides in the presence of cyclohexene included a carbinol by photoaddition of cyclohexene to the "in ring" carbonyl group of N-acety1phthalimide and a novel photoproducts which can formally be seen as insertion of cyclohexene between the two "in ring" carbonyl groups of N-acetyl-3.4,5.6-tetrachlorophthalimide with elimination of acetamide.