Gene probes developed locally for both enteric Adenoviruses 40 and 41 were used to determine whether these viruses were present in both raw and treated waters. Approximately sixty water samples were concentrated by ultrafiltration and analysed directly for the presence of enteric adenoviruses. Three pretreatment techniques, namely sephadex columns, cellulose fibre and GenecleanTM were tested for the removal of inhibitory substances from concentrated water samples. The effect of chlorine treatment on viral detection using gene probe hybridization was also examined by exposing adenoviruses to chlorine concentrations of up to 20mg/l for 1 hour. Enteric adenoviruses were detected in up to 59% of both raw and treated waters analysed. Cellulose fibre and GenecleanTM were found to successfully remove inhibitory substances from concentrated raw waters. Viral DNA was detected after exposure to a range of chlorine concentrations indicating that the viruses detected in the treated waters may have been inactivated virus particles.