Herein, we report on direct preparation of macroporous polyimide (PI) films with pores distributing on one side, the method of which relies on sedimentation of ceramic spheres in polyamic acid (PAA) solutions in a gravitational field and imidization of PAA/ceramic spheres mixtures to obtain PI/ceramic spheres hybrid films followed by curing in dilute hydrofluoric (HF) acid. In this strategy, the curing of the hybrid films in HF acid leads to the formation of pores. The introduction of pores makes the room-temperature dielectric constants of the macroporous films lower than that of pure PI film. Moreover, the macroporous PI films have improved Young's moduli and higher thermal stability in nitrogen atmosphere. (c) 2007 Wiley Periodicals, Inc.