Experiments investigated the effect of various media constituents (Fe2+, PO4 3-, and NH4 +) on H2 evolution during anaerobic iron corrosion. At pH 7.0 when sulfide was absent, Fe2+ did not have much influence on H2 release rates, whereas higher PO4 3- and NH4 + promoted H2 evolution. If present, soluble sulfide controlled H2 release rates in the solutions with Fe2+ or PO4 3-. However, if both soluble sulfide and NH4 + were present at high concentrations, very low rates of H2 release were observed. A simplistic empirical model was developed to fit data on corrosion rates from previous research with sulfate-reducing bacteria (SRB). The best fit empirical coefficients were consistent with trends noted in this work and provided a good fit to previous researchdata, supporting the idea that water chemistry is more important to previous results obtained in the presence of SRB than is commonly realized. The practical relevance of previous studies is of concern given the atypical levels of nutrients in media used. Includes 30 references, tables, figures.