The aim of this study was to develop equations which best predict individual-tree total volume and mercahntable volume for T. grandis in Costa Rica. A total of 112 trees with ages between 2 and 47 years and breast height diameter (dbh) between 2.4 and 58.7 cm were felled for stem analysis. Linear and non-linear regression analyses were used to model the relaitonship of total volume with dbh, with dbh and total height, and with age. The study also included merchantable volume equations that estimate merchantable volume to a minimum top diameter or bole length. The equations tested in this study fitted the observed data well. Other models, developed elsewhere, tended to overestimate the stem volume, especially at dbh bigger or the same 30cm. General geometric cylinder volume equations combined with a Stem Form Factor of 0.45 (widely used for T. grandis) were less precise than regression models when applied to this data set. Model validation with an independent data set suggested that the models should be calibrated with local data when grat accuracy is required (error less than 10%).