Abstract: The cat is often a difficult subject to anaesthetize quietly and smoothly, for restraint may provoke violent struggling and sometimes frenzy. High amount of ascorbic acid probably has similar physiological properties as amphetamine in the central nervous system depression and impairment of nervous system functional have been reported due to deficiency of this water-soluble vitamin. Based on this background, this study was designed to determine the effects of ascorbic acid on Ketamine anesthesia in cats. The trial included 16 cats (9 males and 7 females) were used. They were randomized into 4 groups of four cats each (A-D) and Ketamine 5% (Trittau, Germany) (30 mg kg^-1) was administered intravenously in to each cats in group D. Four cats each in groups A-C received 5, 10 and 20 mg kg^-1 of ascorbic acid, respectively. Five minutes after premedication with ascorbic acid, the animals were treated with Ketamine. The onset and duration of anesthesia as well as vital parameters were observed and recorded. The results are presented as means±SEM changes in the control and experimental values were compared for statistical significance using ANOVA and a probability level at 5% as levels of significant. There were significant decrease in the onset (A and B groups), heart rate (A, C and D) and respiratory rate (A and D groups), respectively (p<0.05). There was also observed significant increase in duration of anaesthesia (A-C groups), respectively (p<0.05). The change in the rectal temperature of cats treated was significant (p<0.05). This results suggest that ascorbic acid at 10 mg kg^-1 administration prior to Ketamine treatment could be use to decrease onset and increase the duration of anaesthesia in cats.