To the yarn manufacturer, the presence of neps in the yarn has always been a concern in terms of the nep's impact on the yarn appearance and dyeability. Until recently neps have not been studied in terms of their possible influence on yarn strength and breaking frequency. It has been the influence of cotton fiber properties of strength, length, and fineness, on rotor spun yarn strength that has been well documented. The aim of this study is to determine if neps have an influence on rotor spun yarn strength. Using commercially processed 19s count 100% cotton yarn for the study, yarn was examined for the presence of neps along the yarn length. Once identified, the nep was removed from the yarn strand at the center of an 18 inch sample length. The sample contained only one nep within it's specified length. Once collected the neps were examined an classified into four treatment groups. These groups were based on the type of nep; fibrous or seed coat, and location; outside the yarn structure or inside the yarn structure. A control yarn sample was collected that did not have a nep within it's yarn length. This sample was used for comparative analysis. Yarn samples were broken on a Instron Tensile Tester at a continuous rate of extension. The mean maximum breaking load was analyzed using the two sample T-test. Variances of the maximum breaking load was analyzed using the two sample F-test. Breaking distances from the nep point were measured and percent frequency graphs were generated for each nep group. Three replications of the study were performed. Results of the data analysis demonstrated that neps within the yarn structure, whether fibrous or seed coat, had no statistically significant influence on breaking load means or variance. Fibrous neps and seed coat neps inside the yarn structure did demonstrate a higher percentage of breaks at the nep point, suggesting that the neps in these two groups created weak places in the yarn structure.