Integrally skinned asymmetric crosslinked polyimide (PI) nanofiltration membranes suitable for organic solvent nanofiltration (OSN) were formed via the phase inversion method. A better understanding of how membrane formation parameters (such as composition of the dope solution, the evaporation step, and chemical properties of the polymer) affect membrane performance (flux and rejection) was sought. The findings were reported in three parts. In this paper. Part A of the study, the importance of the choice of polyimide and solvent system was studied. Membranes prepared from Ultem 1000 and Matrimid 5218 were much more open as compared to membranes prepared from P84 and HT P84. Increasing share of 1,4-dioxane used as a co-solvent did not improve rejection of membranes prepared from Ultem 1000 and Matrimid 5218. An introduction of a simple tool based on mutual solubility parameters allowed to qualitatively predict the effect of polyimide choice and solvent composition used in the dope solution on membrane performance. Lower value of the introduced total solubility parameter was very well correlated with lower rejection. (C) 2011 Elsevier B.V. All rights reserved.