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A metallographic and fractographic study by scanning electronmicroscopy study of the nucleation and evolution of hydrogen induced cracking (HIC)growth was done. The HIC cracks were induced by cathodic charging and its growthwas monitored by straight beam ultrasonic mapping, so the nucleation sites as well asthe cracking evolution could be identified and measured. The results showed that thereare inclusions that nucleate HIC in very short times and others nucleate cracks onlyafter hundreds of hours after hydrogen charging, but the early nucleation sites areusually clusters of inclusions, rather than individual ones. It was observed that the HICgrowth is composed of two mechanisms: the growth of individual cracks and theinterconnection of several cracks to form larger cracks that continue growingthemselves and by interconnecting with other cracks. The interconnection mechanismcan be by direct interconnection of coplanar cracks or by out of plane interconnection,where crack deflection plays a very important role. The study is completed withobservations of the crack path and the kinetics of HIC growth for both, overall andindividual HIC.