Contamination on cotton fibers is one of the most important problems that shows itself on yarn and fabric. Contamination usually consists of plant leafs, parts, etc. on the cotton and this situation occurs during the harvesting and transporting. Also contamination occurs by bale pieces such as burlap, nylon and polypropylene residues. Developed technologies are using for selection of the foreign material in blowroom and bobbin processes, but it is not possible to completely remove the foreign material from the yarn. In general, the amount of foreign material in the local cotton is more than the US cotton.  In this study, yarn production is made in the same specifications with local and US cotton, then yarn foreign material cuttings on bobbin machine and yarn quality values are compared. According to the results, it is seen that yarns produced by US cotton have less contamination than the yarns produced by local cotton. With this situation it is determined that, despite less contamination, yarn technical values of US cotton is worse than local cotton.