The successes of the long-duration MDA/NASA test programs for advanced life-support systems conducted prior to 1971 were highly dependent on the selection and training of both the test crews that remained inside the test chamber throughout the test periods and the outside operating staff. The operating staff was responsible for overall test performance, crew safety monitoring, operation and maintenance of the test facilities, and collection and maintenance of data. A selection, training, and certification program was developed and performed to ensure operating staff members had the correct technical skills and could work effectively together with the inside crew. A training program was designed to ensure that each selected operating staff member was capable of performing all assigned functions and was sufficiently cross-trained to serve at other positions on a contingency basis, if needed. The certification program consisted of a system of operational readiness reviews and pretest activities to verify the proficiency of the operating staff and their compatibility with the internal crew during normal, contingency, and emergency operations.This paper describes the selection procedures, assignments, certification requirements, and training for the chamber test operating staff. Emphasis in this paper is on the MDA/NASA 90-day chamber test. Summary descriptions of the facilities, support equipment, and operating procedures used for the test are also provided.