A randomized controlled trial of the effect of zinc sulphate on neurosensory hearing loss in infants. In a randomized clinical trial we studied the effect of zinc sulphate on the aetiology of neurosensory hearing loss in a cohort of neonates with unexplained hearing loss in southern Nigeria. Infants with bilateral neurosensory hearing loss and a gestational age of more than 35 weeks were recruited, but infants born with congenital abnormalities were excluded. Infants were randomized to receive either oral zinc sulphate or placebo for 3 months. Hearing was evaluated at birth, 1 and 6 months using auditory brainstem responses. The study was completed in a total of 72 infants, 36 in each of the treatment arms, and no child was lost to follow up. A total of 52 (72.2%) neonates had neurosensory hearing loss and 16 (23%) showed deterioration by at least 15 decibels in the intervention group as compared to 13 (20.4%) and one (1.5%) in the placebo group. The overall proportion of children showing improvement by more than 20 decibels was 30% for zinc sulphate (9/30) and 5% (1/20) for placebo. Zinc sulphate was statistically associated with improvement of hearing loss (OR = 1.8, 95% CI 0.8-4.1, p = 0.036). Zinc sulphate administration may contribute to the treatment of neurosensory hearing loss. We conclude that further study is warranted.