Disinfection by-products have been the subject of intense study in the water treatment community due to the established adverse health effects of many known by-products and the postulated adverse health effects of many other known and unknown by-products. Aldehydes are one such group of by-products, containing compounds of both known and postulated health effects. This thesis explores the formation of simple alkyl aldehydes due to different disinfectants; these relationships are important because they can aid in determining possible by-product formation of potentially harmful substances with a particular disinfectant or disinfectant combination. Compounds such as these biodegrade easily, presenting a potential for microbial growth in distribution systems. Water samples were taken from the Atkins Reservoir in Massachusetts and treated at different concentrations with four disinfectants: ozone, chlorine, chlorine dioxide, and ferrate. The samples were analyzed for formaldehyde, glyoxal, methyl glyoxal, and propanal. The highest concentrations produced were for formaldehyde, followed by glyoxal. The greatest concentrations resulted from oxidation using ozone or chlorine dioxide. Ferrate and chlorine produced similar concentrations of these aldehydes. Water samples that had been fortified with sodium bromide before addition of ozone, chlorine dioxide, or ferrate produced higher concentrations than any three of those disinfectants alone. For samples treated with chlorine, longer contact times produced slightly higher increases in formaldehyde and glyoxal concentrations but had no distinct effect on methyl glyoxal. Propanal concentrations were low and barely detectable throughout the study so little information was reported on it.