MAbs such as daclizumab have shown promising results in the treatment of corticosteroid-resistant aGVHD. Data describing the efficacy of MAbs in children are limited. We describe the efficacy of daclizumab in children with corticosteroid-resistant aGVHD. Seventeen children (0.4-16.2 yr) received daclizumab for aGVHD. Safety was evaluated in all 17. Response was evaluated in the 15 children who received a full course of daclizumab. A PR was defined as improvement of aGVHD symptoms in at least one organ without worsening in other organs. We observed an overall response rate (CR plus PR) of 40% (6/15). Four children had a CR and two had a PR. aGVHD involving the gut had the highest response rate (five of 10; 50%). Adverse effects attributed to daclizumab were limited to an episode of reactive arthritis. Mortality was high (47%; eight of 17) though five of the six responders to daclizumab survived. The mean length of follow-up in the surviving nine patients was 32 months (range seven to 48). We conclude that daclizumab is effective in the treatment of children with corticosteroid-resistant aGVHD, especially in patients with gut involvement.