During the anaerobic corrosion of steel, hydrogen sulphide (H2S) evolution by the Sulphate-Reducing Bacteria (SRB) promotes hydrogen absorption by enhancing cathodic hydrogen evolution and inhibiting the combination of hydrogen atoms. While the effects of hydrogen damage are well known, it is unclear whether surface SRB films influence hydrogen absorption any differently to the separate effects of H2S. Also, for particularly hydrogen sensitive metals in soured environments, there is some doubt regarding what constitutes a safe but effective level of cathodic protection. Using the electrochemical technique of Devanathan and Stachurski, special apparatus were used to monitor hydrogen permeation through steel foils exposed simultaneously to cells and cell-free dialysates in batch cultures of either Desulfovibrio vulgaris (Woolwich) or Desulfovibrio desulfuricans (Norway 4). Further experiments were performed using applied potentials of -850mV (SCE) and -1000mV (SCE), and polarisation scans were performed on replicate steel specimens under the same conditions. Changes in pH, Eh, cell numbers and H2S levels were monitored during SRB growth. Following a period of SRB growth and H2S evolution, hydrogen permeation currents rose rapidly and then peaked. Subsequent hydrogen permeation declined markedly, and the potential of freely corroding specimens became less active. This was interpreted as evidence for anodic polarisation, which was consistent with the types of adherent sulphide films present. Polarisation data confirmed that partially protective films became established within the first 24 hours of SRB growth, and that corrosion was under anodic control. Most importance has been placed on the observation that a surface hydrogen concentration (0.066ppm) generated during cathodic protection at -850mV (SCE) was up to 10 times Co values obtained by freely corroding specimens. A further lowering in potential to -1000mV (SCE) resulted in a doubling or tripling in hydrogen permeation rate. The presence of SRB cells at the steel surface appeared to influence neither the peak hydrogen permeation rate, nor the protectiveness afforded by corrosion product films.