We show that whether trade is one-way or two-way depends on wage strategies adopted by trade unions. The union’s wage strategy choices themselves depend upon the conditions under which trade takes place, as well as upon the characteristics of both the labour and the product markets in the trading countries. The impact of economic integration on union choices and therefore upon both labour market and trade outcomes is shown to vary according to the nature of the prevailing trade regime. We generate testable hypotheses and discuss the implications for the development of econometric tests of these hypotheses.