The syntheses of 5H-cyclohepta[b]pyrIdin-5-one, 9H-cyclo- hepta[b]pyridine-9-one, 5H-cyclohepta[c]pyridin-5-one and 9H-cyclo hepta[c]pyridin-9-one are reported. The photolysis of these compounds and 4H-cyclohepta[b]furan -4-one are reported together with a proposed structure for the photodimer from the photolysis of 5H-cyclohepta[b]pyridin-5-one in methanol. Reactivity indices have been calculated by Hückel Molecular Orbital calculations for the pyridotropones, 5H-benzocyclohepten- -5-one and methoxybenzocycloheptenones and by Self-Consistent Field methods for the pyridotropones and the benzotropone. The results are then compared with experimental findings. The ultra-violet spectra for the pyridotropones and the benzotropone have been calculated by S.C.F.-C.I. methods and compared with the observed spectra. S.C.F.-C.I. calculations have also been carried out on 5H-benzocyclohepten-5-one describing possible excited state intermediates formed during photochemical cylization.