Crack initiation and propagation in sour environments have been studied as part of understanding sulfide stress cracking mechanism. This research evaluated crack growth rate of two heats of C110 under different loading modes and exposed to two different solutions with different buffer capacities (NACE Solution B and C). There was no effect of decreasing K profile on the crack growth rate behavior in either environment on either heat. The Kth estimated from DCB tests for heat I in solution C were consistent with the values measured using the constant K test method. However, in solution B, stable cracking was observed under constant K conditions at K values lower than the Kth measured in the DCB tests. The difference in the crack growth rate behavior between solution B and solution C is likely associated with the different buffer capacities of the two solutions. Solution B is a more stable buffer (acetic acid/sodium acetate) and hence is likely to support significantly higher metal dissolution rates by supporting higher cathodic current densities on the crack flanks.