Samples were removed from 6 veal, 35 A-maturity and 12 C-maturity bovine longissimus (L) muscles at 1 and 7 days postmortem. Myofibril fragmentation index (MFI), Warner-Bratzler (W-B) shear-force, sensory panel evaluation and sodium dodecyl sulfate (SDS) polyacrylamide gels of myofibrils were determined on muscle samples and steaks. Correlation coefficients between MFI and W-B shear-force were -0.95, -0.73 and -0.65 and, between MFI and sensory tenderness, were 0.97, 0.75 and 0.72 for steaks postmortem aged for 7 days at 2°C from veal, A-maturity and C-maturity carcasses, respectively. SDS-polyacrylamide gels showed that the intensity of the 30,000-dalton component corresponded to the tenderness level of the steaks. These results demonstrate that MFI accounts for about 50% of the variation in tenderness and that myofibril fragmentation and the intensity of the 30,000-dalton component offer potential usefulness as indices of tenderness.