The trial B-NHL 2013 is a collaborative prospective, multi-national, multi-center, randomized trial with participating centers of the NHL-BFM group (Austria, Switzerland, Czech Republic, Germany) and the Scandinavian NOPHO group (Denmark, Finland, Norway, Sweden). The aim of the trial is to evaluate the role of rituximab in the treatment of mature aggressive B-cell Non-Hodgkin lymphoma and leukemia (B-NHL and B-AL) in children and adolescents.