The material properties of ten 2-O suture materials were evaluated tensiometrically at time = 0 and again after 6 weeks incubation in rats. All suture material was incubated and tested without knots. Specialized machinery was used with a custom securing apparatus to pull suture material apart at constant speed. Stress-strain curves were derived, and from these strength, toughness, strain at rupture, and elastic modulus were determined. Sutures tested included Vicryl [poly(glycolide-lactide)], Dexon (polyglycolic acid), Ethibond (polyester), silk, plain gut, chromic gut, Maxon (polyglyconate), PDS (polydioxanone), nylon, and Prolene (polypropylene). Elastic modulus was greatest for braided, least for monofilament, and intermediate for gut sutures, regardless of chemical composition (ANOVA, P = 0.0001). Strength, strain, and toughness decreased in all of the sutures over time in vivo with the exception of braided polyester (Ethibond), which remained stable. Silk demonstrated the least strength and toughness while PDS and Maxon were the strongest and toughest at time = 0. Vicryl, Dexon, and gut sutures were absorbed to the point that they could not be tested after 6 weeks in vivo. Performance tables are provided for all sutures.