Tubulars used in underbalanced sour drilling can be subjected to more severe environmental conditions than encountered in traditional overbalanced drilling. This paper describes testing conducted with the double cantilever beam technique in simulated environments, discusses performance of representative drill string tubulars and possible mitigation in the context of development of industry guidelines. Keywords: sulfide stress cracking, underbalanced drilling, H2S, tubulars, double cantilever beam, steel, TM0177