Abstract
Bacteria and/or bovine faecal matter were introduced into cultures of pathogenic free‐living amoebae with Baquacil. They created a biochemical oxygen demand and/or an increased Baquacil demand. Baquacil was shown to be amoebicidal under all but 1 of the conditions tested which simulated those likely to be encountered in swimming pools. Axenically and monoxenically cultured amoebae were used, and the latter exerted the greater Baquacil demand.