The aim of this study was to compare the effects of two different anesthetic techniques on the acid base balance in bitches. Research was carried out on 20 bitches randomly divided into two groups. In group A general anaesthesia was induced by intravenous application of ketamine and diazepam, and maintained with an additional intravenous bolus of ketamine. In group B a combination of propofol and ketamine was used for induction of anaestesia. General anaesthesia was maintained with N 2 O and O 2 in a range of 1:1 in combination with 2% isoflurane. Animals in both groups were kept on spontaneous ventilation. Arterial blood for blood gas analysis was taken at two time points (3 and 45 min. after induction of anaesthesia, respectively). Group A had a significantly (P<0.05) higher pH value than Group B at 45 min. The pCO 2 was significantly (P<0.05) lower in group A than in group B at 3 and 45 min, respectively. There was also a significant difference in values of pO 2 between the groups at 3 and 45 min. The pO 2 was lower in group A than in group B. Group B had a significantly (P<0.05) higher HCO 3 -value than Group A at 45 min. Volatile anaesthesia minimally disturbs acid-base balance, and oxygen access capability is better.