A fully automated thermomechanical fatigue test system capable of extremely sensitive crack growth measurements was developed. This system was used to conduct thermomechanical fatigue tests on titanium matrix composites to study the crack growth behavior throughout cyclic testing as well as during individual loading cycles. Experiments were performed in bending on specimens with a realistic initial defect, a corner crack geometry, for composite materials. Data was collected during the experiments using the reversing dc electrical potential method and changes in crack dimensions were determined via an inverse solution to the electrical potential field. Isothermal, in-phase and out-of-phase thermomechanical fatigue crack growth experiments were conducted with test temperatures ranging from 204°C to 538°C.