This experiment was designed to evaluate the effects of ractopamine hydrochloride (RAC) on muscle quality and sensory attributes of three genetic lines of swine. Berkshire (n = 76), Duroc (n = 81), and high-lean commercial crossbred (n = 75) barrows and gilts were fed either a standard commercial diet or a diet supplemented with RAC (10 ppm). The trial was conducted using a randomized complete block design, with animals blocked according to litter, gender, and starting weight. Pigs were started on the experimental diet at approximately 85.1 kg and remained on test for 28 d. Pigs were harvested at a commercial abattoir and muscle quality measurements taken at 24 and 48 h post-mortem. Quality traits measured were visual firmness and wetness (24 h), pH (24 h and 48 h), visual marbling and color (48 h), Minolta color scores (24 h and 48 h), and water-holding capacity (48 h). Sensory attributes of the loin were assessed by a three-person trained sensory panel to subjectively evaluate juiciness, tenderness, and chewiness (sustained tenderness). Objective measurements of tenderness (Instron), percentage cooking loss, and chemically separated loin lipid content (intramuscular fat, IMF) were also obtained. The inclusion of RAC in the diet had no significant effect on muscle quality assessments, sensory attributes, or objective measures of palatability. Differences were observed between genetic lines for most quality and sensory traits, with Berkshire pigs generally being superior. Loins from barrows were firmer (P < .05), higher in 48 h pH (P < .05), lower percentage drip loss (P < .05), and had improved sensory tenderness scores (P < .05) when compared with loins from gilts. For IMF, genetic line x treatment and genetic line x gender interactions were detected. Berkshire pigs fed RAC had a lower (P < .05) percentage of IMF than control pigs. The purebred barrows (Berkshire and Duroc) had higher (P < .001 and P < .05, respectively) IMF compared with the respective purebred gilts, with no gender difference for IMF observed in the high-lean line. The results from this experiment indicate that feeding RAC does not affect muscle quality or palatability characteristics.