A phase I/II trial for the treatment of children with recurrent malignant diseases with the oral histone deacetylase (HDAC) inhibitor vorinostat is open and recruiting patients since May 2012 (http://clinicaltrials.gov/ct2/show/NCT01422499). We and other groups have shown that HDACs propagate growth and survival of many pediatric cancer cells, while inhibiting diffentiation and programmed cell death. The targeted inhibition of HDACs could therefore be a novel therapeutic strategy in the treatment of pediatric tumors. Children and adolescents (3-18 years of age) who did not respond to standard first or second line therapy, including patients with recurrent solid tumors, lymphomas or leukemias, can be treated in this trial. The patients are treated according to an intra-individual dose escalation concept in 10 centers throughout Germany. The trial is funded by the German Children´s Cancer Foundation (Deutsche Kinderkrebsstiftung), the drug vorinostat is being supplied by MSD Sharp & Dohme GmbH. Small children will receive individually prepared oral drug suspensions. A synopsis can be downloaded here.