Microspheres (MCs) of different polymers, such as poly(ether sulfone) (PES), polyetheretherketone with card, with and without pore formers, were prepared by the non-solventinduced phase separation (NIPS) process. The polymers were solubilized in different types of solvents, such as dimethyl formamide (DMF), dimethylsulfoxide (DMSO), N-methylpyrrolidone, and gamma -butyrolactone as a dispersed phase, whereas dodecane, isopropanol, water, and sodium dodecyl sulfate were used as continuous phases. The technique yielded asymmetric and symmetric porous, spongy, or finger-like, spherical MCs having a diameter tailored by the monopore film pore size employed. The influence of polymer and pore former (polyvinylpyrrolidone k17), the continuous phase composition and operating membrane process conditions, and solvent uptake behavior of different solvents are studied in detail. The operative conditions and chemical compositions are correlated with the spherical nature, structural interaction, pore size, porosity, and morphology of the MCs prepared. Ternary phase diagrams were drawn for PES/DMF and PES/DMSO using different alcohols, such as butanol, isopropanol, ethanol, and methanol. BET (BrunauerEmmetTeller) surface analysis also provided information about the surface of MCs. MCs with different diameters and porosities are obtained by controlling the concentration of the dispersed phase polymer concentration, used during the preparation, and diameter of the monopore film. (c) 2012 Wiley Periodicals, Inc. Adv Polym Techn 31: 231241, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21281