Core-spun yarns are defined, and the main objective of core spinning is to combine the aesthetic and comfort properties of natural fibres with easy care and strength properties of synthetic filaments. Double roving feed (DRF) is generally advocated for core spinning. This study attempts to establish the reinforcing effect of nylon multifilament core on the tensile properties of cotton and viscose rayon covered core-spun yarns. Raw materials are identified and methods of yarn production described. Yarn samples were tested for tenacity and breaking extension using Instron tensile tester interfaced with an automatic plotter. Other tests conducted investigated the variation of single yarn tenacity and breaking extension, the effect of yarn breaking time and the effect of specimen length. Abrasion resistance was also examined. Five principal conclusions are summarized, including the strengthening of the yarns with the incorporation of nylon multifilament as the core component.