An increasing number of children suffering from cancer has been treated successfully during the last 25 years using therapy protocols of the Gesellschaft für Pädiatrische Onkologie und Hämatologie. The patients had to undergo an interdisciplinary treatment modality and a mostly intensive chemotherapy. Late effects could result from this approach for the now 20,000 survivors in the Federal Republik of Germany. The executive committee of the GPOH founded a working group for the detection of late effects stretching over all therapy studies. The first report of this group describes a spectrum of relevant late effects and proposes investigations for their detection.