A mechanistic computer model which predicts growth of flue-cured tobacco was written in PASCAL and run on an 80386 personal computer. Plots of NC2326 and K399, grown in Oxford, NC, were destructively sampled every week from transplant to final harvest. Measurements included fresh weights and dry weights of leaf, stem, stalk, and roots, leaf surface area, and nitrogen/alkaloid content. Air and soil temperature, solar radiation, and rainfall/irrigation were continuously monitored. These data, along with data from the literature, were used to develop equations describing rate of leaf appearance; photosynthesis; respiration; partitioning of available carbon to root, stem, stalk, and leaf; growth of leaves at each stalk position; timing of flowering; and timing of harvest. The model currently predicts dry weight of stem stalk, and leaf (by stalk position) on a daily basis based primarily on daily minimum and maximum temperatures. Predicted and observed values were in agreement. Future versions of the model will include the impact of solar radiation and rainfall and predict leaf chemistry and biomass. Long-range plans include the addition of submodels of important pests such as root-knot nematode, the black shank fungus, and the Granville wilt bacterium.