Background: The tissue-suture interface remains the most common site of failure in rotator cuff repairs. Improving stitch strengths may lead to lower failure rates. Purpose: To compare biomechanical properties of 3 self-cinching stitches to the simple, mattress, modified Mason-Allen, and massive cuff stitches. Study Design: Controlled laboratory study. Methods: In sum, 336 sheep infraspinatus tendon grafts were randomized among 7 stitches. Each graft was cyclically loaded on a mechanical testing system from 5 to 30 N for 20 cycles and then loaded to failure. A mixed-effect multivariate regression model was used to test significance of suture type on cyclic elongation, peak-to-peak displacement, and ultimate load. Estimated means and standard deviations are reported from the regression model. Results: Ultimate load for the simple stitch was significantly lower than for the other stitches. The lasso-loop and mattress stitch demonstrated similar ultimate loads. The double-cinch had a higher ultimate load than the lasso-loop or mattress stitch, although it was significantly weaker than the modified Mason-Allen, lasso-mattress, and massive cuff. The lasso-mattress had a superior ultimate load to the modified Mason-Allen and a similar ultimate load to the massive cuff stitch. One significant difference was found in cyclic elongation (1.42 mm for the simple to 1.80 mm for the double-cinch), and the cinching mechanism accounted for 0.2-mm higher elongation. Conclusion: Self-cinching stitches lead to superior tissue-holding strength at the tissue-suture interface when compared with equivalent non-self-cinching stitches. Self-cinching stitches have greater elongation values. How these differences in cyclic elongation clinically influence gap formation at the repair site is unknown. The greater displacement seen in the self-cinching stitches is a potential concern because minimal gap formation is desired for a strong repair. Clinical Relevance: The lasso-loop stitch is a stronger alternative to a simple stitch, and the double-cinch and lasso-mattress stitches are stronger alternatives to a mattress stitch. © 2011 The Author(s).