Campylobacter are the primary cause of food poisoning in the UK and many other countries so, because chicken are recognised as one of the main routes by which this organism gets into the human food chain, there is considerable interest in identifying potential sources of Campylobacter on the farm. One potential source of infection is water, which may also be a means by which the organism is transmitted through the flock following initial infection. Studies into the role of water in Campylobacter infection of chickens have identified the importance of factors such as biofilm in protecting the organisms and, potentially, the viable but non-culturable form (VNC) of Campylobacter. While difficulties in identifying the VNC form in field outbreaks may have led to an underestimate of the importance of water as a risk factor there are contradictory views regarding the ability of the VNC form to cause infection under field conditions. Producers may treat drinking water with a range of products to reduce the number of microbial contaminants, Campylobacter included, that reach the growing bird in the drinking water. Examples of products used by producers include chlorine, chlorine dioxide, organic acids, peracetic acid and hydrogen peroxide. The efficacy of these products differs depending on the environment in which they are used, pH for example having a significant effect on the efficacy of chlorine. If the full benefits of drinking water treatment are to be realised then further evidence is required, in terms of the effects on the normal production parameters such as weight gain, feed conversion efficiency, flock uniformity as well as on the prevalence of infection such as that caused by Campylobacter.