Cluster randomized controlled trials (cluster RCTs) randomize whole clusters of individuals in testing two or more competing interventions. Here we will present the ethical problems raised by cluster RCTs concerning their effect on inequality. We argue that some inequalities generated by cluster RCTs are larger in scope than those generated from individual RCTs. We also argue that any cluster RCT-generated inequalities, which divide groups rather than individuals, are more problematic in type than the inequalities created in individual RCTs. These concerns (...) should be taken into consideration when designing research at the cluster level, and those conducting the research should consider modified research design strategies in cases where they believe the risk of generating inequalities is large. (shrink)