A comprehensive and systematic study of the stress-strain behavior of seven synthetic absorbable and nonabsorbable sutures was conducted. The purpose of the study was to provide detailed mechanical information on suture materials in order to assist surgeons in their selection of adequate sutures for specific surgical applications. The use of a yarn grip, newly designed specifically for fibrous materials, eliminated several difficulties imposed by conventional grips, and resulted in more dependable mechanical properties. A wide range of stress-strain characteristics was observed in the tested sutures. Suture materials of similar nominal properties may behave quite differently in their stress-strain relationship. This was true of sutures of the same chemical nature as well as of different geometric construction, such as Ethilon vs. Nurolon. Larger differences in stress-strain curves were observed after the yield point with yarn grips than with conventional grips. The unique shape of the stress-strain curves, and the associated data derived from them, provide better information in the discrimination between suture materials.