Determining whether human performance is affected by environmental stressors generally requires repeated-measures using tests which possess both stability and reliability. Cognitive and psychomotor tests are becoming popular testing devices, particularly in computer-based modes of administration. However, to date, there is no standardized battery for the study of environmental stressors which has proven itself over repeated-measures applications. In this study, three experiments were performed to evaluate the stability, reliability, and cross-test correlations of nine tests selected from the Automated Performance Test System (APTS), and 15 tests selected from the Unified Tri-Service Cognitive Performance Assessment Battery (UTC-PAB). These two batteries are in various stages of development. The APTS battery has been developed largely under NASA and NSF sponsorship. The UTC-PAB is a DOD-Mandated battery. Cognition, human performance, performance tests, psychomotor skills, test batteries.