The eflects of midazolam·ketamine (M·K) and xylazine-ketamine (X-K) combinations on arterial blood pressures and blood gases 01 12 dogs were evaluated in this study. All baseline measurements were made before the anesthesia as baseline values, and all measurements were repeated at 15, 30, 60, 90, and 120 minutes intervals after the anesthesia. While the heart and breathing rates increased in the M-K group of dogs, there was a decrease in the X·K group of dogs with the statistical significant difference (1)<0.05). The difference between the sistolic and di· astolic arterial blood pressures was not statistically significant between the two group of dogs. On the other hand, The mean blood pressures at the 90 and 120 minutes were statistically significant (p<0.05). While there was no sta· tistically significant difference on the arterial PaC02 and Pa02, there was a statistically significant difference on pH at the 15 (p