ABSTRACT: Background: To obtain an accurate diagnosis, children with hearing impairment could be examined by auditory brainstem response test. Young children are usually uncooperative and could not be examined without sedation. The most commonly used sedative is chloral hydrate. Some investigators used melatonin as an alternative sedative. Our study aimed to evaluate the effect of melatonin as adjuvant when added to chloral hydrate.  Methods: The study was conducted at the Clinic for Hearing, Balance and Communication, Mosul, Iraq, from July to December 2018, and has been approved by the regional Research Ethics Committee with a design of the un-blinded randomized clinical trial. Parents provided a written informed consent. Two hundred and fifty-four children aged 8 months-7 years attending for auditory brainstem response test were allocated randomly to two groups. The group A children as controls (n=150), were receiving chloral hydrate oral dose 50mg/kg, while the group B cases (n=104), were receiving melatonin 0.1mg/kg plus chloral hydrate 50mg/kg. Both groups were compared in sleep latency, success rate of sedation within 30 minutes, as well as sleep duration. Relative risk (RR), t-test and chi-square were used.  Results: Within 30 minutes of the initial dose intake, the group of the combined melatonin and chloral hydrate achieved a higher success rate in the sleep induction than the group of the chloral hydrate, (n=98, 94.2% versus n=112, 74.6%), RR=1.262, P<0. 001.Conclusion: Melatonin could enhance the efficacy of chloral hydrate when added to it, as an adjuvant agent.