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The growth of young, even-aged, monospecific and homogeneous stands of Pinus taeda L. are evaluated and simulated with the Diffusion Processes simulation technique. The used data were obtained from measurements over individual trees in 1993 and 1996 (6th and 9th years) in a spacing test of Pinus taeda L. at farm “Fazenda Lageado”, Jaguariaíva-PR, from the Pisa Florestal company. Diameter class models to obtain estimations of relative diameter increment, variance of relative diameter increment, and mortality were previously fitted. The equations were fitted with linear regression techniques (Classic Least Squares Method) and non-linear regression techniques (Marquardt algorithm). The diffusion equations construction, in spite of requiring previous statistical estimations, don’t present great difficulty to be implemented for Pinus taeda stands. The diameter distributions simulated with diffusion processes were found to be harmonic and coherent. In the case of the precocious growth evaluation and simulation treated in this study, an outstanding factor of the diffusion processes is the use of regression techniques. The regression techniques, linear or non-linear, mitigate any discrepancies caused by the young age of the stands and the small size of the sampling units.