wildlife food and cover, and erosion control among other uses. Tree basal area growth data spanning 39 years are available on 15 species from eight permanent plots in the Luquillo Experimental Forest. The complexity of the rain forest challenges current forest stand modeling techniques. As a starting point individual tree basal area growth is modeled using the Chapman-Richards function constrained for hypothetical maximum tree size. In addition to initial tree diameter or basal area, significant explanatory variables are crown class, topographic position and degree of ground incline. Plots illustrate the differing growth patterns of the 15 tropical mixed/moist forest species. Two species exhibit exceptional growth. Buchenavia capitata (Vahl) Eichl. has basal area growth peaking at 87 cm2 year- ‘. The Manilkara bidentata (A. DC.) A. Chev. data show growth rates in excess of 60 cm* year-’ and the Chapman-Richards function indicates growth potential to a peak of 122 cm2 year-‘.