A FORTRAN based simulator, PTAEDA, was developed to model growth in managed loblolly pine (Pin us taeda L.) plantations, using individual trees as the basic growth units. In PTAEDA, trees are assigned coordinate locations in a stand and "grown" annually as a function of their size, the site quality, and the competition from neighbors. Growth increments are adjusted by stochastic elements representing genetic and microsite variability. Mortality is generated stochastically through Bernouli trials. Subroutines were developed to simulate the effects of site preparation, thinning, and fertilization on tree and stand development. Comparisons with published yields showed close agreement for thinned and unthinned old-field plantations. Results indicated that, compared to stand-level models used in the past, the simulator is more flexible in terms of growth and yield estimation and evaluation of alternatives under a wide range of management regimes.