The trade relations between Bangladesh and 4 of its South Asian partners is modeled within a larger macroeconomic model. The macroeconomic model, including the trade functions is estimated econometrically using a single-equation simultaneous method. The results of econometric estimates are very encouraging with exceptionally good fits in most cases. The model also includes an aggregative supply side manifested in a value-added production function reflecting labour surplus in the economy. This makes the model non-Keynesian. It also specifics a non-neoclassical capital accumulation process in the economy. The model is simulated to analyze the macroeconomic effects on the Bangladesh economy, of trade expansion (increase in both exports and imports) with India, Pakistan, Nepal and Sri Lanka. The model permits the effect of imported intermediates from South Asian countries on output to be captured. This is perhaps, the most important contribution of the model. The simulation results show positive gains from increased trade. However, the instruments and institutions required to boost intra-South Asian trade are still weak and have not been addressed in this paper.