AASHTO CSDIM-1, Culvert and Storm Drain System Inspection Guide, First Edition (2020), sets out a standardized procedure for assessing the condition of culverts and storm drains. Opening sections explain why standardized inspection is needed and frame performance in terms of structural integrity, hydraulic performance, and roadside compatibility. Design and performance characteristics are then reviewed, including hydraulic requirements, flexible versus rigid structural behavior, dead and live loads, construction and installation conditions, and durability. The inspection procedure covers inspection types, from initial inventory through routine, special, and damage inspections, and distinguishes person-entry from non-entry internal inspection. Inspector qualifications, training, and standard and nondestructive inspection equipment are also addressed. The guide is written for inspection personnel and the agencies that manage culvert and storm drain inventories.