In the western North Atlantic, some shrimps of the genusPericlimenes interact with fishes. Accoring to prevailing wisdom, these shrimps “clean” the fishes (i.e. they remove parasites, diseased tissue, or detritus from their exposed surfaces). With one exception, the numerous literature entries recite anecdotal evidence. The only report based on empirical studies has dismissed the notion that “cleaner” shrimps perform the services attributed to them, leaving the nature of the relationship unresolved.