A methodology to analyse electrochemical impedance spectroscopy (EIS) data for the study of microbiologically induced corrosion is proposed. The proposed methodology is based on the loss tangent behaviour of EIS spectra for sterile and bacteria-inoculated environments. Loss tangent parameters were obtained by fitting the EIS data to the Cole?Cole dispersion model using a genetic algorithm. Two electrochemical cells were implemented to expose carbon steel probes to sterile and inoculated media for two bacteria consortia, acid-producing bacteria (APB) and sulphate-reducing bacteria (SRB). The APB tests were exposed for 96 h and the SRB tests for 144 h. A microbial count was carried out during each experiment. The EIS spectra were measured during exposure for sterile and inoculated media. The spectra were fitted to a multi Cole?Cole dispersion model, and loss tangent parameters were obtained.