The objective of this study was to examine the effectiveness of CaCl2 infusion in overcoming the toughness of meat associated with dietary administration of a beta- adrenergic agonist (BAA) to lambs. Thirty-two crossbred (1/2 Finnsheep X 1/4 Dorset X 1/4 Rambouillet) wether lambs were randomly assigned to receive 0 or 4 ppm BAA (L644,969; Merck, Sharpe and Dohme Research Laboratories) in a completely mixed, high-concentrate diet for 6 wk. Animals were slaughtered in two groups of 16. At each slaughter time half of each group (0 or 4 ppm BAA) was randomly assigned to CaCl2 infusion. Feeding the BAA decreased (P less than .05) fat thickness, kidney-pelvic fat, yield grade, and marbling and increased (P less than .05) dressing percentage, lean firmness, leg score, and biceps femoris weight. Weight of biceps femoris was 32.8% greater in BAA-fed lambs. Treated, but not infused, lambs were significantly less tender than control lambs after 1, 7, and 14 d of postmortem storage. At 24 h postmortem, BAA-fed lambs had higher (P less than .05) cathepsin B, calcium-dependent protease-II (CDP-II), and CDP inhibitor activities. Calcium chloride infusion increased marbling, decreased lean firmness, increased lean color score, and increased dressing percentage (P less than .05). Infusion of carcasses with CaCl2 decreased (P less than .05) shear force at all postmortem times. Infusion of carcasses with CaCl2 had no effect on cathepsins B and B + L activities, but it had a significant effect on CDP-I, CDP-II, and CDP inhibitor activities.(ABSTRACT TRUNCATED AT 250 WORDS)