OBJECTIVE: To compare the effect of acepromazine on surgical duration and complication rate when compared to medetomidine. STUDY DESIGN: A randomised, prospective clinical study. ANIMAL OR SAMPLE POPULATION: Thirty-two female entire dog. METHODS: Thirty-two female entire dogs undergoing elective laparoscopic ovariectomy (lap-ove). Dogs were randomly assigned to pre-medication Group M (medetomidine, n = 20), or Group A (acepromazine, n = 12). Anaesthesia protocol was standardised and monitored by one anaesthetist. The surgeons were blinded for the group allocation. Time was recorded at predetermined intra-operative points. Surgical difficulty was subjectively assessed intra-operatively, as well as objectively scored following review of the surgical recordings. Procedural complications were recorded. RESULTS: The mean ± SD surgical time from skin incision to removal of both ovaries was 11.8 ± 1.8 minutes and did not differ significantly between the two groups (M: 11.7 ± 1.6, A: 11.9 ± 2.3). Across the entire study population surgical difficulty was assessed as 'easy' in 14 dogs (44%), 'medium' difficulty in 14 dogs (44%) and 'marked' difficulty in four dogs (12%), while complication rate was 12.5% in both groups. There were no significant differences in difficulty or complication rate between groups. CONCLUSION: Choice of pre-medication did not significantly affect any of the outcomes measured. CLINICAL SIGNIFICANCE: Acepromazine may be used for sedation as part of a balanced premedication protocol as an alternative to medetomidine in dogs undergoing laparoscopic ovariectomy without significantly increasing the procedure time, surgical difficulty or complication rate.