This book is intended to provide information on fundamental genetic processes in tropical forests. It is based on lecture notes by the authors prepared for po- graduate students, mainly from tropical countries, of the M.Sc. course “Tropical and International Forestry�at the Faculty of Forest Sciences and Forest Ecology, Georg August University Göttingen, Germany. The intended readership is s- dents, researchers and practitioners interested in the genetic variation of species, in particular forest trees, living in complex forest ecosystems in the tropics. Particular emphasis is placed on the human impact on forest genetic resources in the tropics. Readers should be familiar with basics of classical and molecular genetics such as the structure and function of DNA (double-helix structure, repli- tion), polypeptide synthesis (transcription and translation), and the transm- sion of genetic information during sexual reproduction (“Mendel rules�). This knowledge is easily available from recently published genetics textbooks; we recommend the book by Griffiths et al. (2000). The development of biochemical and molecular marker techniques and their application to species of tropical forests have greatly improved our kno- edge of genetic variation patterns of “wild�plants in the tropics during the last two decades. Many examples in this book are based on gene marker techniques.