Resumo. There is a great demand for wood within tropical natural forests and a scarcity of available data to carry out a management program. It is of great importance, therefore, that growth ring information is being enhanced. The Pantanal of Nhecolândia, sub-region of Pantanal Mato-grossense, may be viewed as one of these regions. Its natural forests are systematically cut to be used as solid wood or fuel, or replaced by cultivated pastures. Peculiar climatic and soil factors of Nhecolandia induce the formation of annual growth rings. This work aims at determining the radial increments of Anadenanthera colubrina var. cebil and Tabebuia impetiginosa by growth ring analysis. Disks from eight trees of Anadenanthera colubrina var. cebil and six of Tabebuia impetiginosa were collected, in July 1996, in Nhumirim Farm, Embrapa Pantanal, located in Nhecolandia sub-region. The trees of Anadenanthera colubrina var. cebil and Tabebuia impetiginosa were 14 to 30 and 15 to 30 years old, respectively. Diameter increment varied from 5.4 to 8.0 mm/year for Anadenanthera colubrina var. cebil and from 4.8 to 11.6 mm/year for Tabebuia impetiginosa. The average estimated time for both species to reach a diameter of 40 cm was 55 years.