An experimental study of crack initiation in solution-treated 316 stainless steel was undertaken to test the validity of the elastic-plastic fracture mechanics parameters, J and crack opening displacement (COD), in the presence of extensive yield. Measurements of the J-integral are obtained for 6.4 to 25-mm-thick compact specimens using the proposed ASTM equation. The latter is shown to give results within 2 percent of those obtained using the original calibration method of Begley and Landes. However, deviations from the proposed crack blunting line, J = 2σ_fΔa are found for this high work-hardening material. Midsection COD is also determined using a rubber infiltration technique. Critical values of the J-integral and COD at crack initiation are shown to be constant independent of plate thickness under plane-strain and non-plane-strain crack-tip conditions as defined by B = 25 to 50 (J_i/σ_f) and B = 25 COD_i. These results are supported by measurements of the surface crack-tip contraction.