Tree-ring analyses and dendrometer measurements were carried out on 37 tree species in a semi-deciduous forest of the Reserva Forestal de Caparo, Venezuela, where the mean annual rainfall is about 1700mm and there is a dry season from December to March. The main purposes of the investigation were to show the seasonality of cambial growth, and the connection between precipitation patterns and tree-ring curves. Long-term rates of wood increment were also estimated. Cambial markings in consecutive years showed that annual rings were formed by many species. The distinctiveness of growth zones was usually greater in deciduous species than in evergreen species, although not all deciduous species had distinct rings. Dendrometer measurements showed that the annual growth rhythm was related to precipitation patterns. Evergreen species tended to show only a short interruption of wood growth (during the later part of the dry season), whereas deciduous species stopped growth completely at the end of the rainy season. For deciduous species, regression analyses showed close relations between tree-ring width and the sum of precipitation outside the rainy seasons (i.e. November to April). Evergreen species reacted to the total annual amount of precipitation. Variation in longest available ring chronology (for Terminalia quianensis) showed little correlation with the El Nino-Southern Oscillation effect. On average trees from natural forests showed relatively constant growth over the entire life span. Plantation trees grew fast up to an age of 15-20 years, but annual increments then decreased to values seen in natural forest trees.