The availability of real time, automated, and reliable atmosphere and water monitoring instrumentation within the timeframe of future manned lunar and Mars missions is vital to the success of the Space Exploration Initiative (SEI). For these missions, with durations measured in years, the environmental control and life support system (ECLSS) must be properly instrumented to assure the crew that the physical, chemical, and biological properties of the atmosphere and water are within ranges that are healthy and safe. The technology for measuring some properties, such as temperature and pressure, is currently available for most applications; however, there are a number of instrumentation functions required for future long duration missions that cannot be performed by current technology.Defining the areas where current instrumentation technology falls short of satisfying potential SEI requirements is a task of immediate importance. Many of these issues involve the automation of measurement processes that currently require crew involvement, and/or the reduction of cycle times to achieve real time measurements. In addition to defining broad concerns, specific technologies must be identified to satisfy future requirements. The process of identifying instrumentation shortcomings and concentrating efforts on the development of technologies which can best eliminate these shortcomings will help ensure that instrumentation needed for SEI missions will be available before planned mission start dates.To lay the groundwork for this definition phase, ECLSS instrumentation is discussed by outlining the types of sensors used on past space flights and indicating where improvements, innovation, and new developments may be required. Factors addressed include cycle time, automation, reliability, and resupply, all of which determine to what degree equipment operation is transparent to the crew. Based on the current knowledge base, emerging new technologies in sensor design are discussed. Instrumentation technologies recommended for future development are identified and prioritized according to the need for particular monitoring functions and the current maturity of applicable technologies.