ABSTRACT Baltic Sea is characterised by anoxic conditions with the proliferation of Sulphate Reducing Bacteria (SRB), which generate significant amounts of H2S in the sediment, and presents drastic seasonal changes in salinity due to ice melting fresh water contribution. H2S in the seabed environment may promote the diffusion of hydrogen into the pipeline steel which needs to be resistant to hydrogen induced damage phenomena (HIC, SSCC). Resistance to HIC was ensured by the selection of an adequate chemical composition for the linepipe steel. During the engineering phase a methodology to quantify the risk of external SSCC was proposed. In order to assess the most reliable design value of H2S concentration and pH for pipeline design, their representative distribution functions in seabed mud were found, and using Montecarlo statistical method the environmental conditions were characterized. Baltic environment, classified following the ISO15156 Ed. 2003 approach, is "mild sour" and therefore it is necessary to qualify the steel material for Region 1. A conservative target test conditions can be assumed: i.e. an H2S concentration and pH, safely representative of 99.99% percentile of the Baltic environment. If steel material is tested and proven resistant to such environment, the residual probability of SSCC susceptibility is equal to the joined probability for a pipeline of a bare metal surface exposed to a seabed mud with a "sour condition" worse than the test condition. In this case, the calculated probability is only 10 - 10 that is acceptable for DNV rules. Beside SSCC phenomena, the presence of elevated concentrations of H2S in sea water and sea sediments has been reported to be detrimental for cathodic protection aluminium sacrificial anodes performance. In order to verify the possibility to adopt aluminium sacrificial anodes for the cathodic protection of a pipeline in H2S environments, a bibliographic study supported by results of a dedicated test campaign has been performed considering different sea water and sediment environments with elevated H2S concentrations.