The aim of this study was to evaluate if metabolic and endocrine adaptive responses to stressful stimuli are influenced by clenbuterol treatment in pigs. Two groups of nine Goland barrows of 167 kg liveweight, fed diets containing 0 (control) or 1 ppm of clenbuterol (clenbuterol-treated) for 40 days, were used. Blood samples were collected by jugular venipuncture the day before (day 40) and at slaughter (day 41). On day 40 clenbuterol-treated pigs had lower levels of thyroxin, tri-iodothyronine, insulin, urea and higher levels of lactate and creatine phosphokinase activity. On day 41, thyroxin concentration was lower and creatine phosphokinase activity higher in clenbuterol-treated pigs than in controls. In response to transport and slaughterhouse procedures, most of the parameters considered both in clenbuterol-treated and in control pigs increased.