In this study, the microbiologically influenced corrosion caused by sulphate-reducing bacteria (SRB) has been studied. The material tested was a drilling pipe steel designated as N-80. Weight loss studies and potential measurements were carried out in two types of culturing solutions, with and without SRB inoculated. From weight loss studies, corrosion rate in SRB inoculated solution has been found to be roughly six fold greater than that in the medium without SRB. Also under the investigated conditions, the effective concentration of biocide necessary to control corrosion of N-80 steel in the presence of SRB, has been found to be at least 500 ppm. (C) 1997 Elsevier Science Ltd.