The thesis presents four papers that begin to analyse transnational monopoly capitalism: (1) Paper One attempts to fill a gap in the literature by examining the impact of intra-firm imports (and exports) on the theoretical specification of the degree of monopoly. It shows that an industry's degree of monopoly need not fall when import penetration-rises. United Kingdom car industry data is used to examine the bias in estimating the degree of monopoly when ignoring intra-firm imports. (2) Paper Two explores the conjectural variation model underlying such a theoretical specification. In particular, it criticises the model for saying little about the determinants of industry equilibrium. It suggests collusion amongst firms focusing on the possibility of joint profit maximisation be given the centre stage, and that equilibrium be analysed in terms of its deviation from the joint maximum, the deviation depending upon firms' retaliatory power, cost functions, and demand functions. (3) Paper Three considers another question arising in (1): why are there transnational corporations? It pursues a Marglinian analysis. A general theoretical framework based upon product market domination is developed, and one aspect of this - labour market domination - is taken up in theoretical and empirical detail. Particular emphasis is given to distributional as against efficiency considerations. Throughout, the analysis is compared to other approaches - for instance, internalisation. (4) Paper Four pursues the theory of the firm by taking up the fundamental issue of who controls firms. In contrast to existing literature, it criticises ex post analysis of' share distributions, and uses a dynamic, historical framework in concluding that owners control firms. This is supported by examining recently reported empirical evidence. Consideration of the M-form organisation, and savings behaviour is used to further discriminate the analysis from managerialism and neoclassicism respectively.