Interfacial void-free Matrimid polyimide (PI) membranes filled with zeolites were prepared by introducing 2,4,6-triaminopyrimidine (TAP). TAP enhanced the contact of zeolite particles with polyimide chains presumably by forming hydrogen bonding between them. The threshold amount of TAP, needed to depress totally the void formation, varied with zeolite type in the order of zeolite 4A approximate to 13X < NaY < 5A < NaSZ390HUA. It was also observed that the threshold amount of TAP could be related with the number of external hydroxyl groups of zeolite particles. The void-free PI/zeolite 13X/TAP membrane showed the higher gas permeability for He, N-2, O-2, CO2 and CH4 with a little expense of permselectivity compared with the PI/TAP membrane, while the PI/zeolite 4A/TAP membrane showed the lower permeability but higher permselectivity. The facilitation ratios of the zeolite-filled PI membranes were strongly affected by the pore size of zeolites. In addition, the molecular sieving effect of zeolites seemed to take place when the kinetic diameter of gas penetrants approached the pore size of zeolites.