|Catalan has two contrasting rhotics: a tap and a trill. The two sounds contrast only between vowels, with the distribution otherwise being predictable. This paper argues for an account of them cast within Dispersion Theory (Flemming 1995), calling on constraints requiring that contrast be maintained, and on others requiring that contrasts be perceptually distinct. The appeal to contrast leads to a simpler and more explanatory account of Catalan rhotics compared to previous ones. The analysis also illustrates how it is possible to incorporate more systematic phonetic detail into phonology without predicting the overgeneration of contrast. This is possible because Dispersion Theory proposes constraints on the output that regulate contrast directly. The importance of phonetic detail to uncovering phonological generalizations in other languages is another emerging theme in recent phonology.