This paper presents an experimental verification of a new two-parameter fracture model based on the equivalent remote biaxial stresses (ERBS) developed by the authors. A detailed comparison is made between the new theory and the constant, K_Ic, approach of linear elastic fracture mechanics (LEFM). Fracture is predicted through a failure curve representing the change in a variable fracture toughness, K_c, with the ERBS ratio, B. The nonsingular term, T, in the series expansion of the near crack-tip transverse stress is included in the model. Experimental results for polymethyl methacrylate (PMMA) show that the theory can account for the effects of geometry on fracture toughness as well as indicate the initiation of crack branching. It is shown that the new criterion predicts failure for PMMA with a 95% confidence zone that is nearly three times smaller than that of the LEFM K_Ic approach.