Polyvinylidene fluoride (PVDF) hollow fibre membranes were prepared via a phase inversion method, using N,N-dimethylacetamide (DMAc) as solvent, lithium perchlorate (LiClO4) as inorganic salt additive and water as the coagulation medium. The phase diagram of the LiClO4/PVDF/DMAc/water quaternary systems was constructed using cloud-point experimental data. With the addition of the LiClO4, the effect of coagulation bath temperature on the structure of membranes was investigated. The gas permeation method was used to estimate the pore size and pore size distribution of the PVDF hollow fibre membrane prepared. Also, the effect of the composition of internal coagulant on the membrane structure was investigated using different ratio of 1-methyl-2-pyrrolidone (NMP)/water mixtures. (c) 2005 Elsevier B.V. All fights reserved.