In this work, single jersey fabrics were produced with different yarn numbers and loop lengths by means of conventional ring-spun and compact ring yarns. Knitted fabrics were subjected to two different relaxation treatments, dry and washing. After relaxation, air permeability of cotton-knitted fabrics with different yarn numbers and loop lengths were determined. In addition, wales per centimeter, courses per centimeter, thickness, and weight of fabric were tested. According to the test results, relaxation type and some fabric structural parameters affected air permeability of single jersey fabrics. Following the washing relaxation, it was found that knitted fabrics became tighter, their weight and thickness were higher, while their air permeability was lower.