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The ability to predict growth and potential yield is essential for planning forest management. Here we developed a narrow size-class diameter model to simulate growth in a mature plantation (age 42 years) of big-leaf mahogany (Swietenia macrophylla King) in a subtropical moist forest in Puerto Rico. We calculated optimal rotation age by means of the biological and economic criteria. The analyses involved diameter measurements over 31 years and a variety of contrasting economic scenarios, which were evaluated by means of the Faustman formula and sensitivity analyses. The optimal biological rotation was 90 years while the optimal economic rotation was 42 years in most of the scenarios, regardless of wood prices and costs of reforestation. Conspicuous changes in the optimal economic rotation were only observed under low interest rates, in which it was prolonged to around 80 years, close to the optimal biological rotation. Abundant natural regeneration and a prolonged biological rotation suggest that other silvicultural systems, rather than traditional clear-cutting and replanting could be adopted. However, to evaluate alternative silvicultural strategies we would need to improve our ability to predict growth. This would require expansion of our database to include information on growth conditions of individual trees and young tree dynamics, as well as size and growth of other species, to model natural regeneration and competition.