The strong presence of large countries in World Trade Organisation (WTO) dispute settlement and the absence of very poor ones have raised concerns that increasing legalisation in the global trading system has not diminished discrimination against less powerful countries as much as expected. This article examines dispute initiations in all WTO member state dyads in 1995–2003 to shed more light on this issue. The analysis suggests that the main driver of dispute initiation is a gravitational one: larger economies and bigger traders are more likely to become involved in trade disputes primarily because their economies are more diversified, and also because greater market size makes them more attractive targets of litigation. While evidence is not found for discriminatory effects against countries with small legal capacity, the results of the article point to a more complex form of power bias – namely a preponderance effect. They suggest that disputes among country dyads including a much more powerful defendant than complainant or vice versa are dealt with outside the WTO. This finding is potentially worrying because it is, arguably, easier to reduce legal capacity differences than to reduce power differences.