This investigation was carried out to estimate and compare comfort properties of blended yarns and knitted fabrics, made with different proportions of cottonised flax and long staple Egyptian cotton (Giza80) using ring spinning system. Cottonised flax was blended in proportions of 30%, 50% and 70% with Giza 80 on draw-frame process. The100% cotton sample was also spun to identical count for comparison purpose. All the samples were spun to 20s, 30s, and 40s (cotton system) at a constant twist multiplier "4.0 , using the ring spinning. Further, yarn samples were suitably waxed and identically knitted into single jersey fabrics with the same construction. Cotton and flax fibers, yarns and knitted fabrics quality properties were tested and evaluated according to ASTM. The main findings could be summarized as follows: 1. The 100% cotton yarns were significantly of higher yarn strength, elongation and evenness “CVm%" and of lower imperfections compared with the cotton/flax blended yarns. 2. A comparison of the bursting strength of the knitted fabric showed that those made from cotton blended with cottonised flax yarns generally have lower bursting strength than those made from 100% cotton yarn. 3. Color Efficiency (K\S) value of the flax-blended knitted fabrics were slightly higher than the cotton knitted fabrics, however the differences between different flax blend ratios were statistically insignificant. 4. Adding flax to cotton knitted fabrics increase the Ultraviolet Protection Factor (UPF) and it could be considered as an effective protection against ultraviolet rays. UPF increased in respective of the increased flax component and decreased yarn count. 5. The results showed that the knitted flax blended fabrics permit more moisture absorption, as compared to the 100% cotton knitted fabrics. This could be attributed to the large diameter of the flax fiber. The difference between cotton and its blends with flax was statistically significant. The air permeability, moisture regain and UPF results revealed that the knitted fabrics made from cotton/cottonised flax are more suitable for summer dress material, because of its high air permeability when dry very rapidly and high UPF.