To study sewer system corrosion, biogenic H2SO4 corrosion of concrete was reproduced in a simulation app. Samples were inoculated with thiobacilli and incubated for 9 mo in a test chamber with a humidity >95% and a temp. of 30 Deg. H2S, S2O32-, and MeSH were tested. H2S at 15 mg/m3 resulted in severe corrosion and the dominant microorganism was Thiobacillus thiooxidans. H2S at 2 mg/m3 produced moderate corrosion and the dominant microorganisms were T. intermedius, T. novellus, and T. neapolitanus. Similar results were obtained with S2O32-, but MeSH at 22 and 2mg/m3 caused negligible corrosion and only heterotrophic bacteria and fungi thrived on the concrete blocks, indicating that MeSH cannot be metabolized by thioobacilli. Field expts. showed that the natural corrosion process can be accelerated >=8 times by the simulation app.