In June 1999, the United Kingdom government amended the Water Supply (Water Quality) regulations regarding the presence of Cryptosporidium oocysts in United Kingdom waters. The new regulations require the water supplier to carry out risk assessments on all its treatment works and establish whether a significant risk of Cryptosporidium oocysts contamination in the water supplied from each works exists. The water supplier is required to notify the Secretary of State of its findings. Those treatment works found to be at risk from Cryptosporidium oocysts contamination must be continuously monitored using the Department of Environment, Transport and the Regions approved concentration method, the Filta Max system. In conjunction with the monitoring program, parameters such as turbidity are monitored. Sudden changes in turbidity are to result in the immediate processing of the Filta Max foam filter. Under normal operating conditions the Filta Max foam filters are to be processed on a daily basis. A limit of less than one Cryptosporidium oocyst per 10L of final water has been implemented. Any waters found to exceed this limit will result in the prosecution of the water supplier. Includes 6 references, figures.