Microorganisms have been shown to survive drinking water disinfection and remain viable in disinfected waters despite the presence of disinfectant residuals. This may be partially due to protection by particulate matter. This paper studies the effects of the presence of particulate matter on disinfection kinetics in comparison to kinetics in particle-free water. Heterotrophic plate count bacteria and Helicobacter pylori were used in inactivation experiments in the presence and absence of soil, corrosion, and wastewater particles. Inactivation of indicator organisms, namely Bacillus subtilis spores and MS2 phages, was also studied using synthetic, demand-free buffered water, in the presence and absence of floc particles. Floc particles were produced using kaolin clay and alum in an attempt to entrap the organisms. The disinfectants assessed in this study include UV, free chlorine, chlorine dioxide, and monochloramine. Results showed that the mere presence of the soil and corrosion particles in the water could affect the inactivation kinetics, decreasing the level of inactivation by up to 1 log in some cases, compared to particle-free water for the same CT. Wastewater particles and coagulated kaolin clay had no effect on microbial inactivation with the disinfectants used in this study. Includes 17 references, tables, figures.