Ithaslongbeenknownthatamphibiaandotherlowerordervertebrates havethecapacitytoregeneratelimbsaswellasdamagedheartsorbrains. Overthepastdecade,therehasbeenamajorchangeinthewaythatthe potentialforregenerationinmammalsisviewed.Earlier,incontrastto the acceptance of regeneration in amphibia, it was generally believed that there was very limited if any capacity for regeneration in many mammalianorgansystemssuchastheheartandbrain.Thediscoveryof tissue-resident adult stem cells and the description of the properties of embryonic stem cells have altered this view. This change in paradigm VI Preface has led to the hope that these discoveries can be harnessed in medical practicetocurechronicdisablingdiseases. The use of tissue-resident adult stem cells depends on the ability to either mobilize them or to convert them from one lineage to another. These problems do not arise with embryonic stem cells. Instead, their useisfraughtwithethicalandpoliticalissuesaswellasthequestionof howtodirecttheirdifferentiationtowardthedesiredcelltype.Whichever approachistaken,issuesofsafetyhavetobeparamount.Inparticular,the roleofstemcellsintumorigenesisiscriticalinassessingtheirpotential clinicalutility. The Ernst Schering Research Foundation and the Riken Center on DevelopmentalBiologyjointlyorganizedaworkshoponThePromises andChallengesofRegenerativeMedicine,whichtookplaceinKobe, Japan on 20-22 October 2004. The purpose of the workshop was to discuss the present state of knowledge and future directions in this important ?eld. Leading basic scientists and clinicians reviewed and discussedseveraltimelytopicswithinthreemainthemes:(1)evolution, development,andregeneration,includingstemcellsinPlanariaandstem cell niches; (2)embryonic and adult stem cells, including adiscussion of the regulatory system in Japan for human embryonic stem cells; and (3) regeneration in speci?c indications including a discussion of the role of stem cells in organs such as the skin, brain, liver, pancreas, cornea,andthecardiovascularsystem.Inaddition,theroleofstemcells in glioblastoma was presented along with the implications for other tumors.