Xylazine (1.1 mg/kg body weight [bwt])-ketamine (2.2 mg/kg bwt) (X/K) anaesthesia was evaluated, in nine Mammoth asses, for effectiveness and compared with two other injectable anaesthetic combinations: xylazine (1.1 mg/kg bwt)-butorphanol (0.044 mg/kg bwt)-ketamine (2.2 mg/kg bwt) (X/B/K); and xylazine (1.1 mg/kg bwt)-tiletamine-zolazepam (1.1 mg/kg bwt) (X/T). All drugs were given intravenously (i.v.). Heart rate, respiratory rate, systolic blood pressure, arterial blood pH, PCO2, PO2, recumbency time and number of attempts to stand were measured. Quality of induction and recovery, muscle relaxation and response to stimulus were evaluated subjectively. One animal did not become recumbent with X/K. Recumbency times were significantly (P < 0.05) different: the shortest time was with X/K (24 mins) and the longest time with X/T (46 mins), with X/B/K, it was 37 mins. Assess required significantly more attempts to stand with X/T (n = 3) than with X/K (n = 1) or X/B/K (n = 2). No significant differences in heart rate, respiratory rate, blood pressure, arterial PO2 or PCO2 were detected between groups. Arterial pH was significantly lower at 15 mins in the X/B/K and X/T groups than in the X/K group. Although X/K generally produced effective immobilisation, the combinations of X/B/K and X/T, appeared to be more satisfactory and relatively safe, and provided longer recumbency times and increased muscle relaxation compared with X/K.