Worlds Apart Trading Together sets out to replace the outdated notion of 'Indo-Roman trade' with a more informed perspective integrating the new findings of the last 30 years. In order to accomplish this, a perspective focusing on concrete demand from the ground up is adopted, also shedding light on the role of the market in long-distance exchange. Accordingly, the analysis conducted demonstrates that an economically highly substantial trade took place between the Mediterranean and the Indian Ocean in the 1st-6th cen. CE, altering patterns of consumption and modes of production in both India, South Arabia and the Roman Empire. Significantly, it can be documented that this trade was organised at the centres of demand and supply, in Rome and India, respectively, by comparable urban associations, the transport in-between being handled by equally well-organised private networks and diasporas of seagoing merchants. Consequently, this study concludes that the institution of the market in Antiquity was able to facilitate trade over very long distances, acting on a scale which had a characteristic impact on the economies of the societies involved, their economic structures converging by adapting to trade and the market.