Cambial dormancy and annual rings in tropical trees are induced by annually occurring dry periods or flooding. Growth periodicity is indicated by the leaf fall behaviour and is connected with an annual periodicity of shoot elongation. Changes in stem diameter are measured with a dendrometer or by measurable differences in the electrical resistance of the cambium. Dendrochronological methods applied to carefully prepared samples can serve as proof of the annual periodicity of growth zones. For this purpose the following methods have been used: cambial wounding, radiocarbon dating, pointer year detection and regression analyses of ring width and climate data. Although X-ray densitometry and the analysis of stable isotopes in rings of tropical trees promise to provide interesting climatological information, the use of these methods remains difficult.