Adenosine 5′-triphosphate (ATP) is known to play a significant role as a neurotransmitter in smooth muscle. There is evidence to show that ATP can cause bladder contractions and may also be involved in the processing of sensory information in the urinary bladder. These effects are likely to be mediated by P2X receptors, namely P2X₁ and P2X₃, respectively. This study set out to investigate their distribution in rat and human urinary bladders. P2X₁ receptor immunoreactivity was found on detrusor muscle fibres and P2X₃ receptor immunoreactivity was found in the urothelium of both species. This is the first demonstration of a non-neuronal localisation for P2X₃ receptors. No clear evidence was found for the presence of P2X₃ receptors on calcitonin gene-related peptide-containing sensory nerves and therefore P2X₃ receptors may not have a direct role in the mediation of sensory responses to ATP in the urinary bladder.