Thirty six U. S. Upland cottons from 1995 crop were processed into 30/1 Ne ring-spun carded yarns. The Mantis^® single fiber tensile properties before and after carding, HVI properties, AFIS^® fiber length, and yarn tenacities were analyzed to evaluate the relationship between fiber and yarn properties and effects of carding. The study has shown that HVI bundle strength, micronaire, single fiber strength, standard deviation of single fiber elongation and fiber length are all found to be significant contributing factors to yarn tenacities. The single fiber tensile properties, tested after carding, were shown to be even better for predicting the resulting yarn tenacities.