This paper utilises a model of a small open economy that produces two traded goods by means of primary factors and a large number of varieties of a non-traded intermediate good. Unlike the traded goods, the production of each variety of the non-traded good is subject to internal economies of scale and monopolistic competition prevails in the intermediate good sector. The presence of internal economies in the intermediate good sector gives rise to external economies in the production of the final good sector. Within the context of the present study, interindustry and intra-industry trade takes place side by side. The model is used to examine the impact of tariffs and changes in factor endowments on allocation of resources and welfare.