Eighteen beef heifers, representing the Bos taurus (Shorthorn), Bos indicus (Afrikaner) and intermediate (Bonsmara) types, were confined to a pen with floor space of 4,6 m2 per heifer. A similar number of heifers on the veld served as a control. Profiles of cortisol levels were obtained during the winter and summer seasons. Pen conditions had no significant effect on cortisol secretions of beef heifers during the winter. The heifers had slightly higher values in the pen than on the veld. No significant differences between breeds were noted, although the Afrikaner heifers generally tended to have the highest cortisol values under pen conditions. Cortisol levels of the Bonsmara heifers fluctuated the most in the pen and on the vcld. Similarly, pen conditions had little effect on plasma cortisol concentrations during the summer season. Penned Afrikaner and Bonsmara heifers had higher levels than their counterparts on the veld, but the opposite was true in respect of the Shorthorn heifers. By extending the penning period from 7 to l4 weeks, cortisol levels in Afrikaner and Bonsmara heifers were not raised. During the last 2 weeks, however, cortisol differences between treatments were noted in Shorthorn heif