High pressure / high temperature (HPHT) wells demand the highest performance equipment and services for the safe and successful completion of these high risk and high cost projects. The demands associated with logging, shoe track isolation, equipment longevity and service life, completion and intervention options, and regulatory compliance push the limits of materials and services. The successful completion of HPHT wells requires advanced materials evaluations, collaboration among many disciplines, and sufficient time for product development and assessment to meet current industry and regulatory standards.The tools utilized in HPHT completions are usually developed to meet the demands of a well or a family of wells. These tools include, but are not limited to, wellbore isolation plugs, production packers, liner hangers, perforating guns, Casing Collar Locators (CCL tools), formation evaluation tools, seal assemblies, and sub-surface safety valves. The methods used for HPHT tool development are evolving, and the development cycles are lengthening, particularly for ultra HPHT applications in which materials screening and stability assessments are required.The development of tools for several recent Gulf of Mexico ultra HPHT wells required a multi-year schedule for development to industry and regulatory requirements. Due due to their extreme depths, ultra HPHT wells typically utilize architecture emphasizing small production casings across production intervals. This complicates cementing procedures, and severely limits product options. From an intervention standpoint, workstring options also become limited. Achieving mechanical success in these applications requires the operator to not only manage traditional resources such as time, people, and cash, but also the development of new high performance technologies in an evolving regulatory environment.What can the industry anticipate for future HPHT wells in terms of architecture, product development, and regulatory challenges? This paper will review the industry's history in these areas, identify current development paradigms and regulatory challenges, and discuss the future challenges in well planning, product development, and regulation.