Ammoximation of cyclic ketones on TS-1 and amorphous SiO2-TiO2 with H2O2 and NH3 was studied. The reactivity of cyclic ketones over TS-1 and amorphous SiO2-TiO2 showed the following order : cycloheptanone > cyclopentanone > cyclohexanone > cyclooctanone. Shape-selective poisoning studies revealed that the active sites of TS-1 for ammoximation of cycloheptanone are mostly inside the molecular sieve. The reactivity of cyclohexanone and methylcyclohexanones over TS-1 followed the order cyclohexanone > 2-methylcyclohexanone is approximately equal to 3-methylcyclohexanone > 2,6-dimethylcyclohexanone, reflecting the difference in the diffusivity among the reactants or products inside TS-1. Besides the diffusivity the reactivity seemed to be affected by the difficulty in access of the carbonyl group to the Ti active site inside the zeolite; from the comparison of reactivity of dimethycyclohexanone isomers, the steric hindrance of the substituent methyl group to the access of carbonyl group was considered to decrease in the following order : beta-equatorial> alpha-equatorial> beta-axial > alpha-axial. Diffusion of cyclohexanone or its oxime has been found to play an important role in the ammoximation when the TS-1 crystals larger than 1.5 mu m were employed as a catalyst. For the TS-1 crystals smaller than 0.3 mu m, the ammoximation activity was independent of the diffusivity factor and was determined by the number of active Ti sites present in the zeolite framework.