A multilateral model of trade with both commodity flows and partial mobility of factor flows is set up. This model is used to develop factor endowment/output relationships as well as commodity/factor price relationships. Welfare consequences of these parametric shifts are examined. The model is built on the customs union framework which involves three countries and both commodity and factor flows. Owing to spillover effects in multilateral trade models, many nontraditional results are obtained. Many developed countries accept skilled and unskilled migrants from other countries. These migrants are generally accepted on a quota system. Moreover, it has been established that an increase in the migrant quota in the presence of factor mobility may raise or lower the output and welfare in the country not receiving migrants. In fact it is shown that the non-migrant receiving country could be immiserized due to loss of capital. The main message of this paper is that in a multilateral trade framework there exist international spillover effects which must be taken into consideration in national policymaking.