Electric Transportation Engineering Corporation (ETEC) Roush Industries, Argonne National Laboratory, and SDI, have been contracted by the US Department of Energy National Energy Transportation Laboratory (NETL) to conduct a program of work to evaluating the durability of a hydrogen internal combustion engine (HICE) design using both accelerated aging tests under laboratory conditions and field tests in diverse fleets. Results of the durability evaluation will be compared to current gasoline internal combustion engine standards and recommendations to reduce durability risk factors developed. The contracted program of work is designed to comprehensively determine long-term HICE durability issues and provide recommendations for reduction of risk associated with these durability issues. An existing state-of-the-art engine design developed and thoroughly performance tested by ETEC and Roush Industries will be the basis of the durability evaluation. The HICE design includes high efficiency supercharging to restore power output lost due to the displacement of combustion air by hydrogen fuel and the use of lean burn operation to minimize NOx production. The engine design also features high efficiency charge intercooling, electronically controlled port injection utilizing a Roush engine management system, and hardened valve sets and faces. These features are incorporated into a 6.0 liter V-8 engine producing 200 horsepower, while maintaining NOx emissions below that of the base gasoline engine (EPA Bin II Tier 7) and producing zero green house gases. This engine will be tested in a Roush Industries engine dynamometer laboratory for 1,000 hours under high stress conditions simulating over 100,000 miles of on-road operation. At the completion of laboratory testing, the test engine will be disassembled and inspected for wear and identification of potential durability issues. Additionally, eight (8) Chevrolet 1500HD pickup trucks, converted with engines identical to the dynamometer test engine, will be used to conduct field-testing of engine durability. These vehicles will be operated in diverse fleets, managed by SDI, for a period of 24 months with the objective of achieving 24,000 miles of operation for each vehicle. During field-testing, the eight durability test vehicles will be closely monitored using periodic maintenance inspections, analysis of engine oil, and periodic emissions tests conducted by Argonne National Laboratory. This data will be evaluated in detail for external evidence of engine degradation. At the completion of field-testing, each durability test engine will be disassembled and inspected for wear and identification of potential durability issues. Inspection reports from laboratory and field durability test engines will be reviewed in conjunction with data from field test operations to establish durability metrics of the HICE engine design. Additionally, durability and life limiting issues will be analyzed and recommendations developed to improve durability and extend engine life. The results of these analyses will present a comprehensive evaluation of HICE durability issues over a wide range of operating conditions, providing direction for future HICE development work. This paper will present results to date for the program including data from both dynamometer and field-testing. HICE durability issues discovered through testing will be the focus of this real-world results presentation.