UK government policy now officially encourages an attitude of 'zero tolerance' towards aggression against health care staff. This study examines levels of such tolerance amongst a group of mental health care staff and associations between tolerance and other occupational and stress factors. Thirty-seven staff completed a Tolerance Scale (from the Perceptions of Aggression Scale) and the Maslach Burnout Inventory. Tolerance for aggression was higher amongst more experienced staff (P < 0.01) and high tolerance was associated with low emotional exhaustion, low depersonalization and high personal accomplishment (P < 0.01). Some staff endorse positive statements about patient aggression and a tolerant attitude may be linked to low burnout. Nurse attitudes to patient aggression therefore are complex and do not necessarily equate with an approach of 'zero tolerance'.