The US Environmental Protection Agency (EPA) conducted an Arsenic Demonstration Program whereby the Agency purchased, installed, and evaluated the performance and cost of 50 small water arsenic removal treatment systems in the USA. A major goal of the program was to collect high-quality cost data (capital and operational and maintenance (O&M)) from the long-term operation (1–4 years) of these systems. The technologies consisted of adsorptive media (AM), iron removal (IR), coagulation/filtration (C/F), ion exchange (IX), reverse osmosis, and point-of-use devices, which reduced the arsenic to less than the EPA maximum contaminant level of 10 μg/L. This paper presents the capital and O&M cost of 48 treatment systems ranging in size from 10 to 770 gal/min (gpm) (38–2,915 L/min). The capital cost of the systems ranged from $477 to $6,171 per gpm ($126–$1,632 per L/min) of design flow and the O&M cost from $0.07 to $22.88 per 1,000 gal ($0.02–$6.05 per 1,000 L) of treated water. AM had a lower capital, but a higher O&M cost than IR, C/F, and IX. The media replacement cost for the AM systems averaged 80% of the O&M cost and was the main cause of the higher O&M cost of the AM systems.