Modellers usually define groups of species to deal with tree species diversity in tropical rainforests. They may be ecological groups with a biological interest or commercial categories with a practical interest. At M'Baïki station in the Central African Republic, seven groups of species are defined at the intersect of five ecological groups and five commercial categories. The ecological groups were obtained by a cluster analysis based on species diameter growth rates, their mortality rates and recruitment rates. A forest dynamics matrix model was then built to assess the relevance of the groups. The stationary state of the stand is well predicted by the model except for one group that appears to pool species with contrasted ecological behaviours.