The mechanisms of sulfide stress cracking (SSC) of grade X60 Iinepipe steels produced by thermomechanical controlled processing (TMCP) have been investigated by applying acoustic emission testing to the NACE TM0177-96 method A tensile test. This method enables the interruption of the test before failure, allowing the observation of the development of subcritical damage as a function of microstructure. The results are interpreted in terms of a correlation between local ftilure mode and microstructural features, with cracking obeying the kinetics described by acoustic emission. Apart from the successful application of acoustic emission testing to the NACE TM0177-96 method A tensile test, this test method has also been shown to reveal Stress-Oriented Hydrogen Induced Cracking (SOHIC) in susceptible microstructure.