 The protocol ALL-REZ BFM 2002 aims at the optimization of treatment for children with relapsed acute lymphoblastic leukemia. The primary objective of study ALL-REZ BFM 2002 is the randomized comparison of a lower dosed and less intensive, but continuous consolidation therapy with conventional therapy administered in treatment blocks. Outcome measures are the reduction of minimal residual disease MRD, event-free and overall survival, and the toxicity associated with each treatment strategy. 