Different types of afferent nerve fibres were identified in the mouse bladder sub-urothelium. At the bladder base the sub-urothelium is more densely innervated than the lateral wall. CGRP and NF afferent nerve fibres in the muscle layer probably relay afferent input to external ganglia located near the bladder base. The identification of different afferent nerves in the sub-urothelium suggests a functional heterogeneity of the afferent nerve fibres in the urinary bladder.