Bolaina (Guazuma crinita Mart., Malvaceae) and capirona (Calycophyllum spruceanum (Benth.) Hook. f. ex K. Schum., Rubiaceae) are fast-growing Amazonian timber trees. In Peru, they are increasingly being used in agroforestry systems and plantations, and interest in developing improved germplasm is growing. However, tree improvement incurs both direct costs and interest costs on investments; because of this, early selection is of interest. We examine the efficiency of early selection 13 or 17 months after field trial establishment. These are compared with selection after 49 or 53 months using two efficiency metrics: one based on discounted response to selection per unit of present value of cost, and the second on net discounted revenues, using discount rates of 5%, 10%, and 15%. Our metrics differed from those used in previous studies by taking into account direct costs, as well as costs of capital.Wefound that in most scenarios, early selection was attractive, partly due to direct cost savings. We conclude that in evaluating the efficiency of early selection, lack of consideration of direct costs may produce erroneous results. We also explore some general implications of the results.