The effect of postmortem time of calcium chloride (CaCl 2 ) injection in conjunction with postmortem aging was determined on 16 beef semimembranosus muscles. Each muscle was cut into four equal segments that were randomly assigned: (1) no injection (control); (2) CaCl 2 at 1 h postmortem; (3) CaCl 2 at 12 h postmortem; or (4) CaCl 2 at 24 h postmortem. Samples were injected with a 0.3 m solution of CaCl 2 at 10% by weight. At 24 h postmortem, each segment was divided into two pieces that were randomly assigned to either a 10-day aging period (2 o C) or to frozen storage (-29 o C). Shear force values were higher (P < 0.01) in control samples compared with injected samples and increased linearly (P < 0.05) with time of injection. Drip loss was lower (P < 0.01) in control samples compared with injected samples. A linear (P < 0.05) effect was found for the increases in cooking and total loss due to injection time. Aging decreased (P < 0.05) shear force values and cooking loss. CaCl 2 injection at 1 h postmortem was most effective in reducing shear force values and preventing excessive moisture loss. However, injection at 12 or 24 h postmortem was also effective in lowering shear force values.