This chapter reviews the one‐carbon compounds with chlorinated, brominated, or iodinated substituted side groups. At ambient temperatures, methyl chloride and methyl bromide are gases; iodoform and methylene chlorobromide are solids; and the remaining seven chemicals in this chapter are volatile, nonflammable liquids. The nonflammability has been an important property for the uses of these chemicals as solvents. Most, if not all, of the chemicals in this chapter are produced in closed‐system facilities. Three of the chemicals (methyl bromide, carbon tetrachloride, and methylene chlorobromide) are ozone‐depleting substances and are tightly regulated under the Montreal Protocol on Substances that Deplete the Ozone Layer. Thus, these chemicals are restricted to feedstock or intermediate uses where, by definition, it is used and entirely consumed, except for trace quantities, and certain exempt applications. For the other chemicals in this chapter, the primary, if not exclusive, uses are as feedstocks or intermediates in the production of other chemicals, the exception being methyl iodide.