['The aim of this study was to evaluate whether a deficit in vitamin D (VD) is associated with an increased risk of recurrent acute otitis media (AOM) and whether VD supplementation is effective in reducing the number of AOM episodes in otitis-prone children.', 'A total of 116 children with a history of recurrent AOM (≥3 episodes in preceding 6 months or ≥4 episodes in preceding 12 months) were prospectively and blindly randomized to receive oral VD 1000 IU/d or placebo for 4 months. Episodes of AOM were monitored for 6 months.', 'Fifty-eight children received placebo and 58 with similar characteristics were treated with VD. The number of children experiencing ≥1 AOM episode during the study period was significantly lower in the treatment group (26 versus 38; P = 0.03). There was a marked difference in the number of children who developed uncomplicated AOM (P < 0.001), but no difference in the number of children with ≥1 episode of spontaneous otorrhea. The likelihood of AOM was significantly reduced in the patients whose serum VD concentrations were ≥30\u2009ng/mL.'] Does vitamin D supplementation reduce the risk of acute otitis media in otitis-prone children?