Chlorinated and brominated haloacetaldehydes (HALs) are considered the 3rd largest class of disinfection by-products (DBPs) by weight. The iodinated HAL, iodoacetaldehyde, has been recently reported as an emerging DBP in finished drinking waters. Overall, iodinated DBPs, e.g., iodoacetic acids, iodoacetamides, and iodonitriles, are among the most genotoxic of all DBPs identified. In this context, this chapter reviews the analytical methods available to date to determine HALs in water, and the concentrations at which they are present in finished drinking waters. Since systematic toxicological effects have been only investigated for selected chloro- and bromo- HALs, a comparative study of the genotoxicity and cytotoxicity of this DBP class to mammalian cells is also presented.