Maintaining pipeline integrity is crucial in the oil & gas industry and when pipeline defects are detected or pipeline failures occur understanding the cause of these events is of utmost importance. Corrosion can have multiple causes and one of these is microbiologically influenced corrosion or MIC. Accurate detection and quantification of corrosion associated microorganisms requires that samples should be obtained and analyzed as quickly as possible when microbial growth tests are used. However MIC is not always considered when beginning an investigation of a pipe segment that is removed from service. It is not uncommon to have a pipe segment removed from service and sitting in a warehouse for days or even months before the possible involvement of MIC is considered. In this event microbial growth tests can’t be used but genetic testing can be employed to detect and quantify bacteria particularly if under-deposit corrosion and/or deep pits are present. This presentation will discuss several case histories of the use of both microbial growth testing and genetic testing (quantitative polymerase chain reaction or qPCR) to examine the microbial population in fresh and not-so-fresh samples of corroded pipe. Examples of both internal and external pipeline corrosion will be discussed.