The performance of a cleanroom garment in the operating environment of a semiconductor fabrication facility is determined by the properties of the garment fabric and the garment design. Ideally, the garment fabric should be highly permeable to water vapor and essentially impermeable to particles. The design of the garment should minimize the discharge of particles generated by the wearer into the cleanroom air. This paper describes a three-part test method for cleanroom garments to determine water vapor transmission through the garment fabric, particle penetration through the garment fabric under specified conditions of pressure drop and velocity, and the reduction in particle generation and discharge into the cleanroom by the garment. The performance of some typical cleanroom garments as measured by this test method is described and compared.