. 1997. Effect of trenbolene acetate/estradiol implants and estrus suppression on growth performance and carcass characteristics of beef heifers. Can. J. Anim. Sci. 77: 325-328. The effects of estrus suppression (none, oral melengestrol acetate (0.4 mg d -1 ) or ovariectomy via Willis spay technique) and an anabolic implant (none or Synovex Plus ® ) on growth performance and carcass characteristics were determined using 90 beef heifers of composite breeding in a 2 × 3 factorial experiment conducted in the last 50 d before slaughter. Spaying caused no morbidity or mortality and resulted in average daily gains (1.37 kg d -1 ) comparable to heifers fed melengestrol acetate (1.33 kg d -1 ). Implanting improved (P < 0.05) feed efficiency and increased (P < 0.05) animal gain, ribeye area, carcass weight and yield and reduced (P < 0.05) intramuscular fat deposition but estrus suppression did not. Method of estrus suppression did not influence (P > 0.05) carcass traits. Spaying and implanting represent an effective means of improving returns from heifers, even late in the finishing period.