Secretion systems are specialized in transport of proteins, DNA or nutrients across the cell envelope of bacteria and enable them to communicate with their environment. The chaperone-usher (CU) pathway is used for assembly and secretion of a large family of long adhesive protein polymers, termed pili, and is widespread among Gram-negative pathogens [1]. Moreover, recent evidence has indicated that CU secretion systems are also involved in sporulation [2,3]. In this review we focus on the structural biology of the paradigmatic type 1 and P pili CU systems encoded by uropathogenic Escherichia coli (UPEC), where recent progress has provided unprecedented insights into pilus assembly and secretion mechanism. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.