The effects of two commonly used drugs for anaesthesia in the domestic cat, ketamine and medetomidine, on features of electroejaculated semen and on sperm flow in this species were evaluated performing three experiments. This is the first study about these topics in the domestic cat. In Experiment 1, ketamine or medetomidine effects on cat sperm quality after collection by electroejaculation (E.E.) have been assessed in nine animals. Results showed that mean sperm concentration was significantly higher (p<0.01) after medetomidine than after ketamine administration. In Experiment 2, ketamine or medetomidine effects on sperm flow in 12 electroejaculated cats were studied. Mean sperm concentration and mean total number of spermatozoa resulted significantly higher (p<0.01) in medetomidine than in ketamine treated animals. The number of spermatozoa displaced in urethra was significantly higher (p<0.01) using medetomidine. No significant differences were observed in percentages of retrograde flow. In Experiment 3, ketamine or medetomidine effects on urethral sperm flow, without any stimulation for sperm collection, were evaluated. Data obtained showed a significantly higher (p<0.05) number of spermatozoa displaced in urethra after medetomidine than after ketamine injection. In conclusion, E.E. in the cat after medetomidine administration determined a higher number of spermatozoa per ejaculate than after ketamine administration, with a good pharmacological restriction and without increasing sperm retrograde flow.