Water is a possible route of transmission of Mycobacterium avium subsp. paratuberculosis (Map) from cattle and other ruminants to humans. This is compounded by the fact that Map has been shown to survive elements of the water treatment process, e.g. chlorination, as well as surviving for protracted periods in the environment. When some microbial populations are subjected to a non-lethal primary stress, which is then removed before a secondary stress is applied, the microbial populations can exhibit elevated resistance to the secondary stress. This phenomenon is termed cross-protection. This study was concerned with the effect of nutrient starvation, to which Map would be exposed in water, on chlorine resistance. Water is generally of low nutrient status, which could be considered as a primary stress, followed by a second stress of chlorination. In starvation studies, stationary phase cultures of Map (strain NCTC 8578) were added to duplicate tubes containing 50 ml of distilled water to give a final cell concentration of approximately 5.5 x 10⁶ CFU/ml. Cultures were subjected to nutrient starvation for 24, 48, 72 and 96 hours. Starved and control (freshly inoculated) cultures were then subjected to chlorine disinfectant (0.5, 1.0 and 2.0(g/ml) for 15 and 30 minutes. The results showed a highly significant difference (P < 0.001) in chlorine resistance between the control and nutrient starved cultures. However, in respect of starvation time there was not found to be a significant difference in log10 survival until 96 h when the survival decreased significantly. Survival of nutrient starved cultures ranged from 86.4% after 24 h to 84.7% after 96 h. This work indicates that Map does not appear to exhibit cross-protection when subjected to at least 96h nutrient starvation.