Aims: The main objective of our study was to assess the persistence of Mycobacterium avium in an oligotrophic environment such as bottled groundwater. Methods and Results: Filtered groundwater samples were spiked with washed Myco. avium suspension and stored in dark and under static conditions, at 20 degrees C, for 3 months in 500 ml PET bottles. The loss of Myco. avium cultivability was slow in water. On the contrary, after a 3-month storage at 20 degrees C, growth of attached cells was observed and cell adhesiveness to the PET wall increased with time. It could probably be because of the presence of an extracellular matrix. Conclusions: This study has shown the great stability of Myco. avium in bulk water as well as their adhesiveness and their growth on a PET bottle wall in an oligotrophic environment. Significance and Impact of the Study: Slowly growing mycobacteria are well adapted to oligotrophic environments such as groundwater. As they stick very well to surfaces, they could be used for determining the efficiency of the cleaning of contaminated surfaces.