Here we present how the surface and some filtration properties of PVC microfiltration membranes are affected by controlled and well-defined modification by ion-plasma treatment in the kinetic region of the high voltage (HVGD) or normal glow discharge (NGD) in air. The surface energy and work of adhesion of the samples were calculated from the contact angle with both polar (H2O) and nonpolar (CH2I2) liquid measurement data. The surface morphology was observed by SEM and the surface chemical composition was analyzed by ESCA. The trans-membrane water flux, the average pore size, and the pore-size distribution as well as the "bubble point" were used to control the effect of the ion-plasma treatment on the filtration properties of the PVC microfiltration membranes. Two characteristic regions of the ion-plasma treatment in air were found in our experiments where the surface properties and filtration characteristics of the membranes are extremely changed: at a pressure of 10-15 Pa in the region of the HVGD and at a pressure of 100-120 Pa in the region of the NGD. It was shown that the ion-plasma treatment in air is an effective technological method for regulation of some important surface and filtration properties of PVC microfiltration membranes. (C) 2003 Wiley Periodicals, Inc.