In cattle, the behavioural expression of fear in response to stressful events is commonly referred to as temperament. Temperament is important for the safety of stock persons and for the welfare or cattle during handling. Temperament can also affect growth, carcass and beef quality characteristics (King et al., 2006, Cafe et al., 2008). Primary physiological responses to stress in animals are the activation of the sympatho-adrenal-medullary (SAM) and hypothalamo-pituitary-adrenal (HPA) axes. Exogenous stimulation or challenge of the HPA axis with adrenocorticotropin (ACTH) is used to assess BPA axis reactivity in cattle (Verkerk et al., 1994). Although it is likely that temperament is related to stress-susceptibility (Curley et al., 2008), and that temperament modifies performance via this mechanism (Ferguson et al., 2006), this assumption requires further scientific testing. In this paper we report findings on the physiological response or cattle differing in temperament, and also on hormonal growth promotant (HGP) status, to routine handling followed by an ACTH challenge.