An automated fatigue and fracture toughness testing control system is described that is based on a Sun 3/180 workstation computer running under the UNIX operating system. Real-time difficulties associated with UNIX have been overcome with a unique combination of software and modified data acquisition hardware that results in a system not requiring conventional analog-to-digital (A/D) and digital-to-analog (D/A) device drivers. The control system software subroutines utilize the multitasking feature of UNIX to permit plotting, computations, and A/D operations to run simultaneously with D/A output. Inputs to the system are primarily through a mouse-driven, menu-based window methodology. The program currently contains four versatile cyclic loading sequences for fatigue crack growth and LEFM and EPFM fracture evaluations that can be applied to five commonly utilized specimen geometries. The software and hardware system has been demonstrated and validated for numerous tests using various materials and specimen types.