Chloramination which is used in South Australia to control the growth of Naegleria fowleri, was investigated to see if it would also control that of Legionella pneumophila. It was found that L. pneumophila was more sensitive than Escherichia coli to monochloramine. At 1.0 mg/l, a 99% kill of L. pneumophila was achieved in 15 min compared with 37 min for a 99% kill of E. coli. Combined with the stability of monochloramine, even at elevated temperatures, the results suggest that this disinfectant would control the growth of L. pneumophila in water distribution systems.