& objectives: Supplying healthy drinking water is one of the important goals in societies and achieving to development depends on the health of society members. Therefore, the current study examined the chlorination and residual chlorine measurement in drinking water distribution system of Ilam city. Methods: In this descriptive cross-sectional study, 40 stations were determined on the water distribution network map and the sampling was then routinely conducted in the view of free residual

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... ine, combined chlorine and the total chlorine in eight stages throughout Ilam city. Sampling and measuring were done in accordance to the standard methods. Analysis of results was performed using Kruskal-Wallis and Wilcoxon statistical tests. Results: The results of Kruskal-Wallis nonparametric test showed no significant difference between free residual chlorine and combined chlorine levels in 40 different sampling stations (sig > 0.05). But, there was a significant difference between average total chlorine in different locations of the city (sig=0.034). The Wilcoxon test showed a significant difference between average free residual chlorine values reported by health service network and measured onsite (sig=0.00). Conclusion: With regard to the direct connection between society health and water quality, implementing appropriate measures can reduce the numbers of undesired residual chlorine in water distribution network of Ilam. In order to do so, monitoring water disinfection by health center experts seems to be necessary.