A number of studies from the US and Europe addressing the epidemiology of NTM in cystic fibrosis has been published. These studies suggest a large variability in the incidence and the nature of the infecting organisms between various regions of the world, and various institutions. While the clinical impression would support a trend of increasing prevalence of NTM in CF parallel to non-CF patients, the absence of repeated studies and the limitations imposed by the inconsistencies amongst centers and regions, does not allow a firm statement on this subject.